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Clinical Outcomes of Zone II Flexor Tendon Repair Depending on Mechanism of Injury
SCIENTIFIC ARTICLE
Clinical Outcomes of Zone II Flexor Tendon Repair Depending on Mechanism of Injury Trevor Starnes, MD, PhD, Rebecca J. Saunders, BSPT, Kenneth R. Means, Jr, MD
Purpose To determine whether mechanism of injury affects outcomes of Zone II flexor tendon repairs. Methods We retrospectively analyzed patients who underwent Zone II flexor tendon repair between 2001 and 2010 with a minimum of 12-month follow-up. Exclusion criteria included fingers with fracture, pulley reconstruction, or flexor tendon bowstringing. The saw group injuries were from saws or from tearing mechanisms; the sharp group had clean transection injuries from knives or glass. At final evaluation, primary outcomes were total passive motion (TPM) and total active motion (TAM) at the proximal interphalangeal and distal interphalangeal joints. Secondary comparisons included strength, Disabilities of the Shoulder, Arm, and Hand (DASH) score, percentage of postoperative tendon rupture, and percentage of patients requiring secondary surgery. The saw group had 13 patients with 17 fingers studied. The sharp group had 21 patients with 24 fingers studied. All patients had primary flexor digitorum profundus repairs in Zone II. Operative records review confirmed for all but 1 patient that flexor digitorum profundus injuries were repaired with a minimum of a 4-strand core suture technique. In the saw group, 9 of 14 fingers with a 50% or greater laceration of flexor digitorum superficialis were repaired; in the sharp group, 15 of 18 such flexor digitorum superficialis injuries were repaired. Average follow-up was 4 years (range, 1–9 y). Results The saw group had significantly less TAM and TPM compared with the sharp group. There was no significant difference in DASH scores, strength measurements, or tendon rupture rates. The rate of secondary surgery was significantly higher in the saw group. Conclusions Tearing types of injury, such as those caused by saws, led to poorer outcomes for Zone II flexor tendon injuries compared with sharp injuries at an average follow-up of 4 years. Our results can be useful when discussing expected outcomes. Mechanism of injury in Zone II flexor tendon lacerations may eventually help define optimal treatment. (J Hand Surg 2012;37A:2532–2540. Copyright © 2012 by the American Society for Surgery of the Hand. All rights reserved.) Type of study/level of evidence Therapeutic III. Key words Outcomes, knife, saw, Zone II flexor tendon repair.
From The Curtis National Hand Center, MedStar Union Memorial Hospital, Baltimore, Maryland. Received for publication September 6, 2011; accepted in revised form September 18, 2012. The authors thank E.F. Shaw Wilgis, MD, for his expertise and mentorship, Lorraine Zellers for serving as research coordinator, Norman Dubin for assistance in statistical analysis, and Anne Mattson for editorial assistance. This study was supported by a grant from The Raymond M. Curtis Research Foundation, The Curtis National Hand Center, Baltimore, Maryland.
2532 䉬 © ASSH 䉬 Published by Elsevier, Inc. All rights reserved.
No benefits in any form have been received or will be received related directly or indirectly to the subject of this article. Corresponding author: Kenneth R. Means Jr, MD, care of Anne Mattson, The Curtis National Hand Center,MedStarUnionMemorialHospital,3333NorthCalvertStreet,JPBM60,Baltimore,MD21218; e-mail: [email protected]. 0363-5023/12/37A12-0013$36.00/0 http://dx.doi.org/10.1016/j.jhsa.2012.09.021
ZONE II FLEXOR TENDONS AND INJURY MECHANISM
especially in Zone II, continues to be a problem with imperfect solutions. Improved surgical repair techniques and rehabilitation protocols have had a positive impact on the outcomes in this patient population.1–5 It is generally accepted that Zone II flexor tendon repairs demonstrate inferior outcomes compared with repairs in other zones.6 –9 Factors that have been shown to play a role in outcomes of flexor tendon repair include associated fracture,1 concomitant nerve injury,10,11 multiple digit injuries, postoperative therapy protocol,12 and a history of smoking.12 We were interested in comparing Zone II flexor tendon repair outcomes based primarily on mechanism of injury (MOI). Historically, investigators have combined multiple MOIs to make generalizations regarding the outcomes for Zone II flexor tendon repair.7,8,13–17 At the 1967 American Society for Surgery of the Hand (ASSH) meeting, Kleinert et al18 reported on primary repair of lacerated flexor tendons in “no man’s land.” A subsequent paper by the group in 197319 summarized their results and techniques. In that landmark paper, the authors stated that “The superior function obtained in repair of sharply incised tendons as opposed to crushing injuries is a well-known fact.”19 Although this statement was no doubt based on a collective vast experience at the time, no direct references or comparative study characteristics based on MOI were listed. Although most surgeons would likely agree with this statement, studies that examine the influence of MOI on outcome for Zone II flexor tendon repairs are limited. The purpose of this study is to determine whether the MOI has an effect on outcomes of Zone II flexor tendon repairs at least 1 year after injury.
F
LEXOR TENDON REPAIR,
METHODS Inclusion and exclusion criteria We completed a retrospective cohort study using data from the medical records of patients who underwent Zone II flexor tendon repair between January 2001 and May 2010 at our institution with at least a 12-month follow-up. Institutional review board approval was granted before we reviewed medical records and contacted patients. Potential subjects were identified by search of Current Procedural Terminology code 26356 from institutional billing records. Only patients who had repair of flexor tendon lacerations in Zone II of the fingers were included. Eight fellowship-trained attending hand surgeons performed the repairs. Surgeons preserved as much of the flexor pulley system as possible but maintained a sufficient amount of the A2 and A4 pulleys, typically at least 50% in our practice, to prevent
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flexor tendon bowstringing and allow postoperative rehabilitation.20,21 Exclusion criteria included patients younger than 18 and older than 75 years, fingers with concomitant fractures, and fingers that required pulley reconstruction or had evidence of flexor tendon bowstringing at the end of the operative procedure. A final evaluation of included patients was completed by a single Certified Hand Therapist who performed all range of motion and strength measurements. From the medical record, we gathered the MOI and surgical treatments provided and confirmed this information at follow-up clinical evaluation. All patients had postoperative hand therapy with various early motion protocols for the digits that were included in the study. Range of motion Following American Medical Association guidelines, the therapist measured active and passive range of motion and flexion contractures for each injured digit at the proximal interphalangeal (PIP) and distal interphalangeal (DIP) joints using a goniometer.22 We calculated total active motion (TAM) and total passive motion (TPM) according to Strickland and Glogovac’s criteria.23 We completed a power analysis before the study and determined that 26 observations per group would give an 80% chance of detecting a clinically relevant 20° difference between the injury groups at the .05 significance level, assuming an SD of 25°.12 Grip and pinch strength The hand therapist measured grip strength using a dynamometer (Jamar; Sammons Preston Rolyan, Bolingbrook, IL) set in position 2. The patient was seated with the elbow joint flexed at 90° and the forearm in the neutral position. The patient’s wrist was maintained between 0° and 30° of extension and 0° and 15° ulnar deviation. The hand therapist asked the patient to grasp the dynamometer with maximal effort for 3 seconds and recorded the average of 3 measurements. The hand therapist performed the lateral pinch strength measurement using a pinch gauge (B&L Engineering, Tustin, CA). The patient was positioned identically as for the grip measurements. The therapist asked the patient to pinch the gauge between her or his thumb pad and the lateral aspect of the index finger middle phalanx with maximal effort for 3 seconds and recorded the average of 3 measurements. Outcome questionnaires We administered the Disability of the Arm, Shoulder and Hand (DASH) outcome questionnaire to each par-
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FIGURE 1: Algorithm results for determining the 2 patient cohorts. CPT, Current Procedural Terminology; FPL, flexor pollicis longus; MOI, mechanism of injury; NHS, National Hand Specialists.
ticipant and scored according to the instructions provided by the Institute for Work and Health (© 2006).24 The hand therapist also obtained a standardized 10point visual analog scale (VAS) score for pain from patients. Statistical analysis We compared demographic data using a chi-square analysis. We performed injured digit analysis, surgical intervention, and complication analysis with the Fisher exact test. We analyzed range of motion, strength, DASH, and VAS data by a t-test, assuming equal variances. We completed a multifactor analysis of variance to determine the relationship between flexor digitorum profundus (FDP)-only repairs and FDP and flexor digitorum superficialis (FDS) repair and TAM outcome. Demographics Our Current Procedural Terminology code search yielded 504 patient records with documented complete laceration of the FDP in Zone II. We reviewed each operative note and excluded 260 patients secondary to concomitant fracture in the injured digit. We excluded 41 patients with flexor pollicis longus tendon repair. We separated the remaining cohort of 203 patients into 2 groups based on MOI (Fig. 1).
The saw group (54 patients) had sawing or tearing MOIs including saw, lathe, fan, and crush mechanisms. The sharp group (149 patients) had clean transection MOIs occurring from knives, glass, metal, and broken porcelain. We attempted to contact the 54 patients in the saw group and a random sample of 104 patients in the sharp group. Thirteen patients (17 fingers) in the saw group and 21 patients (24 fingers) in the sharp group returned for clinical evaluation. The saw group patients had 11 saw injuries, 1 lathe injury, and 1 fan injury. The sharp group patients had 15 knife injuries and 6 glass lacerations. Table 1 presents demographic data for both groups. All patients underwent primary repair of the FDP injury in Zone II. Table 2 presents FDP repair details and associated injuries/surgical interventions in both groups. We did not analyze whether surgeon, FDP repair type, number of FDP core suture strands, type of core suture used, use of an epitendinous suture, and/or associated pulley repair were independent factors with regard to range of motion outcomes because of the significant amount of variation for some categories and limited variation in other categories. One patient’s operative note from the saw group had incomplete information with regard to repair technique. All other patients had documentation of at least a 4-strand core suture repair of
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TABLE 1.
Demographic Data
TABLE 3. Fingers Involved
Saw Group
Sharp Group
Male:female
13:0
14:7
Mean age (y)
47 ⫾ 4
Hand dominance (R:L:A)
11:1:1
High school
5
7
Vocational training
4
College degree
2
Graduate degree
2
2
P
2 (12)
0 (0)
.17
42 ⫾ 3
.30
Dominant middle finger
1 (6)
1 (4)
.99
19:2:0
NS
Dominant ring finger
2 (12)
4 (17)
.99
.82
Dominant small finger
1 (6)
8 (33)
.06
Nondominant index finger
3 (18)
6 (25)
.71
6
Nondominant middle finger
4 (24)
0 (0)
.02
6
Nondominant ring finger
2 (12)
3 (13)
.99
Nondominant small finger
2 (12)
2 (8)
.99
.13
Unskilled manual
0
1
Skilled manual
8
5
Nonmanual/office work
0
2
Professional/management
5
13
Workers comp (Y:N)
2:11
6:15
.44
Tobacco use (Y:N)
2:11
6:15
.38
A, ambidextrous; L, left; NS, not significant; R, right. Bold indicates significant difference (P ⬍ .05).
Injury and Surgical Repairs
FDS repaired
Saw Group (%)
Sharp Group (%)
P
14/17 (82)
18/24 (75)
.99
9/14 (64)
15/18 (83)
.25
Cruciate tendon repair
10/17 (59)
18/24 (75)
.32
Nerve repair
13/17 (77)
10/24 (42)
.03
6/17 (35)
1/24 (4)
13/17 (77)
2/24 (8)
Vascular repair Other injured digits
P
Dominant index finger
Occupation
FDS cut ⱖ 50%
Sharp Group (%)
.02
Education
TABLE 2.
Saw Group (%)
.01 < .001
FDS, flexor digitorum superficialis. Bold indicates significant difference (P ⬍ .05).
each FDP tendon. Of these patients, all except 3 in the saw group also had an epitendinous suture placed in the FDP tendon. In the saw group, there were 10 cruciate, 4 Strickland, and 2 modifiedKessler looped-suture repairs. In the sharp group, there were 18 cruciate, 3 Strickland, and 1 modified-Kessler looped-suture repairs. The major repair type was cruciate for both injury groups, with 59% in the saw group and 75% in the sharp group (P ⫽ .32). One patient in the saw group had repair of the A4 pulley. No other pulley repairs were performed. We did not observe clinically notewor-
Bold indicates significant difference (P ⬍ .05).
thy bowstringing of the finger flexor system for any patients intraoperatively or after surgery. Follow-up averaged 4.7 years ⫾ 0.6 years (range, 1.6 – 8.4) in the saw group and 3.9 years ⫾ 0.5 years (range, 1.0 – 8.6) in the sharp group, which was not a significant difference (P ⫽ .36). Injured digits (Table 3) were similar between the groups except for a statistically significantly increased number of nondominant middle finger injuries in the saw group (P ⫽ .02). There were 25 patients confirmed as having early active flexor tendon protocols (74% [25/34] overall, 81% [17/21] in the sharp group, and 62% [8/13] in the saw group; P ⫽ .25). One patient in each group initially had early modified Duran protocol consisting of passive flexion only for the first 3 weeks (6% [2/34] overall, 5% [1/21] in the sharp group, and 8% [1/13] in the saw group; P ⫽ .99). Three patients in the saw group had early hand therapy, but we could not confirm the exact protocol used (23% [3/13]; P ⫽ .05 compared with the sharp group). There were 2 patients in each group for whom we could not locate initial therapy charts or prescriptions (12% overall [4/34], 10% [(2/21] in the sharp group, and 15% [2/13] in the saw group; P ⫽ .63). RESULTS The TAM for the saw group was significantly worse than that for the sharp group (86° ⫾ 14° vs 114° ⫾ 7°; P ⫽ .05). We compared the percentage of normal TAM between the saw group and the sharp group. Using Strickland and Glogovac’s classification23 of TAM outcomes criteria, we also compared the percentage of excellent, good, fair, and poor results for both groups (Table 4). The saw group fingers also had a statistically
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TABLE 4.
ZONE II FLEXOR TENDONS AND INJURY MECHANISM
Total Active Motion Outcomes Normal TAM (%)
Strickland and Glogovac Excellent (%)
Strickland and Glogovac Good (%)
Strickland and Glogovac Fair (%)
Strickland and Glogovac Poor (%)
Saw group
49 ⫾ 8
3 (18)
2 (12)
3 (18)
9 (53)
Sharp group
65 ⫾ 4
5 (21)
6 (25)
8 (33)
5 (21)
P
.05
.03
.03
TAM ⫽ (active PIP flexion ⫹ active DIP flexion) – (flexion contracture at PIP ⫹ DIP). TPM ⫽ (passive PIP flexion ⫹ passive DIP flexion) – (flexion contracture at PIP ⫹ DIP). Percentage of normal TAM ⫽ TAM/175° ⫻ 100. Bold indicates significant difference (P ⬍ .05).
significantly worse average TPM at the PIP and DIP joints than patients in the sharp group (Fig. 2). There were larger flexion contractures for the combined PIP and DIP joints in the saw group compared with the sharp group, which was also significant (Fig. 2). Table 5 reports the lateral pinch, grip strength, DASH, and VAS pain scores for both groups, for which there were no significant differences other than for uninjured hand grip strength, which was stronger in the saw group. Tendon rupture occurred in 1 of 17 digits in the saw group. No tendon ruptures occurred in the sharp group’s digits (P ⫽ .4). However, a significantly different rate of secondary surgery was evident with the saw group digits requiring secondary surgery in 9 of 17 digits compared with 3 of 24 digits in the sharp group (P ⫽ .01). Secondary surgeries in the saw group included PIP joint arthrodesis in the patient with a postoperative tendon rupture, a cross-finger flap division, tenolysis in 4 digits, and tenolysis and capsulectomy in 3 digits. Secondary surgeries in the sharp group included tenolysis in 2 digits and application of a Digit Widget (Hand Biomechanics Lab, Inc., Sacramento, CA) for flexion contracture in 1 digit. We completed a regression analysis to determine whether FDP-only repair and combined FDP and FDS repair were independent factors with regard to TAM in patients with both tendons cut. We did not have enough power to determine whether the TAM differences we observed favoring repair of both FDP and FDS for the saw group and the sharp group were significant (Fig. 3). DISCUSSION Ever since Kleinert et al18 reported on primary repair of Zone II flexor tendon lacerations in 1967 at the annual ASSH meeting, surgical repair and research have evolved to focus on completing the strongest biomechanical construct with the best patient outcomes. Zone II flexor tendon outcome studies review the techniques of repair within the tendon sheath and emphasize the
importance of meticulous tendon handling techniques. Multiple studies have also focused on postoperative therapy protocols that have advanced from immobilization to early passive flexion motion protocols such as the Kleinert et al25 or Duran and Houser26 protocols to, more recently, early active flexion therapies.12 Multiple Zone II flexor tendon outcome studies have combined various MOIs. Outcomes are worse with concomitant fracture,1 nerve injury,11 and contaminated wounds.1 Kleinert et al19 stated that crush injuries do worse than sharp lacerations. For our study, we attempted to compare Zone II flexor tendon repair outcomes based primarily on MOI. Our study results led us to reject our null hypothesis regarding MOI in relation to range of motion. We have shown inferior outcomes for injuries that occur by a tearing mechanism such as a saw or lathe. There was significantly less TPM and TAM as well as a larger flexion contracture at 4.7 years follow-up in the saw group. These differences may be because of an increase in the severity of injury with a tearing mechanism as compared with a clean transection injury as shown in Table 2. Several potential issues can limit the strength of our conclusions. At our institution, digits with Zone II flexor tendon repair and concomitant digital nerve repair are not rehabilitated any differently from those that do not have nerve injuries. However, the nerve injury itself may be an independent factor for a worse range of motion outcome. Many of our patients were transported to our facility from a considerable distance for their initial surgery and, therefore, did the majority of their therapy at a location closer to their home. The type of postoperative therapy protocol itself could not be included in our analysis of independent factors affecting range of motion but is known to have an effect on overall outcome.12,27,28 The presence of associated injuries in other digits may also have led to slower reha-
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180 160 140 D e 120 g 100 r 80 e e 60 s 40
159.8
P = .02
133.8 Saw Group Sharp Group
20 0 A
Total Passive Moon
140 120 D 100 e g 80 r e 60 e 40 s
P = .05 114.3 86.2
Saw Group Sharp Group
20 0 B
Total Acve Moon
50 45 D e g r e e s
40
P = .005
35 30
39.7
25
Saw Group
20
Sharp Group
15 10
17.2
5 0 C
Flexion Contracture
FIGURE 2: A Average total passive motion (TPM), B total active motion (TAM), and C flexion contracture results and 95% confidence intervals for the Saw Group (saw/tearing injury mechanism) compared with the Sharp Group (sharp injury mechanism).
bilitation protocols or just to poorer outcomes owing to greater overall trauma to the injured hand. Because of the low number of observations in these subgroups, we cannot rule out the possibility that negative findings may be the result of Type II errors. In fact, it may even be likely that the poorer outcomes in the saw group are caused by the greater number of same-digit and other-digit injuries in the same hand. We
also had a relatively large number of surgeons performing different flexor tendon repair techniques with different suture materials. There is limited comparative information about flexor tendon repair techniques and suture material impact on range of motion outcomes. Hwang et al29 performed a biomechanical study and found that suture material did not affect work of flexion whereas repair of both FDP and FDS compared with
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TABLE 5.
ZONE II FLEXOR TENDONS AND INJURY MECHANISM
Strength, DASH, and Pain Outcomes Injured Hand Grip (kg)
Uninjured Hand Grip (kg)
% Uninjured Grip (%)
Injured Hand Lateral Pinch (kg)
Uninjured Hand Lateral Pinch (kg)
% Uninjured Lateral Pinch (%)
DASH
VAS Pain
Saw group
37 ⫾ 3
47 ⫾ 2
84 ⫾ 5
11.0 ⫾ 0.7
11.0 ⫾ 0.6
99 ⫾ 6
16 ⫾ 4
0.9 ⫾ 0.3
Sharp group
34 ⫾ 3
38 ⫾ 2
88 ⫾ 5
9.0 ⫾ 0.5
10.0 ⫾ 0.4
93 ⫾ 3
12 ⫾ 3
1.0 ⫾ 0.4
.3
.03
.59
.06
.07
.37
.47
.83
P
DASH, Disability of the Arm, Shoulder and Hand; VAS, visual analog score. Bold indicates significant difference (P ⬍ .05).
Interaction Plot 140.0
Total Active Motion
120.0 P = .07
100.0 80.0
Saw Sharp
60.0 40.0 20.0 0.0
FDP
FDP+FDS
FIGURE 3: Interaction plot comparing total active motion (TAM) for flexus digitorum profundus (FDP) only versus FDP and flexor digitorum superficialis (FDS) repair for the 2 groups.
FDP repair alone did increase work of flexion. Hoffman et al30 found that Zone II FDP repair with a 6-strand core suture, compared to 2-strand core suture repair, was associated with better range of motion and strength and fewer complications at relatively early 8- to 17week follow-up. In a dog study, Winters et al31 found that 4 different suture techniques did not affect joint range of motion at 3 and 6 weeks after surgery but the 8-strand technique led to a stronger tendon repair than other techniques. Because all of our patients had at least a 4-strand core suture repair of the FDP tendon injury and there was only 1 postoperative flexor tendon rupture, we believe the differences in repair technique are not clinically meaningful. However, we did not design the study to evaluate
repair technique as an independent variable for range of motion outcome, which is another potential weakness of our study. For the 1 patient with incomplete intraoperative documentation about repair technique, we did not observe postoperative flexor tendon rupture. There is controversy regarding repair of both FDP and FDS or just FDP in Zone II flexor tendon lacerations. Previous biomechanical studies have demonstrated that partial or complete FDS excision decreases gliding resistance in Zone II flexor tendon repair.32 Tang33 has also demonstrated this clinically with a nonsignificant trend toward increased TAM in patients in which only the FDP was repaired. However, others have suggested the importance of maintaining at least
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part of the FDS as a gliding bed for the FDP repair to decrease the work of flexion29 or to increase active PIP joint flexion excursion and power. Our study suggests that further research is necessary to define outcomes of FDP repair with or without FDS repair for these types of injuries. Our impression has been that tearing-type injuries, such as those seen from power saws, do worse than clean/sharp tendon injuries even when fractures, nerve injuries, or other digit injuries are not present. For digits with power saw injuries, we may vein graft injured vessels, graft or use synthetic conduits for nerve injuries, and even graft or perform local flaps for soft tissue coverage, yet we typically repair the flexor tendon injuries primarily if the débrided tendon ends can be approximated without excessive tension or digital flexion. This consideration could even be taken to the next level for digits that have bone injury or that are complete replantations. We sought to first determine whether our experience and the literature reports about the poorer outcomes for Zone II flexor tendon repair with these types of injuries are correct. We believe our current study has confirmed this impression at our institution. We tried to eliminate variables, such as fracture and replantation, that would alter our typical postoperative therapy protocol for Zone II flexor tendon repairs. Perhaps consideration of different treatment options, such as delayed tendon grafting as was classically done for all Zone II injuries, is warranted for these injuries or even more severe injuries such as those with fractures, revascularization, or replantation. Some of our most experienced partners believe that the positive results for Zone II repairs reported first by Kleinert and then by many others since have been used to excessively generalize recommendations for primary repair in all or most traumatic cases, regardless of MOI, need for replantation/revascularization, or presence of associated injuries. As a possible practice application, MOI should be considered as another potential factor in outcomes for Zone II flexor injuries. Further study may also involve incorporation of tendon bioengineering principles such as scaffolds, stem cells, or growth factors at the site of injury and repair,2,34 which may lead to improved range of motion, tendon repair strength, and restoration of native tendon tissue regardless of MOI. This study serves as a prognostic guide for patients with these types of injury. It will help guide the surgeon in providing expected outcomes to patients who sustain Zone II flexor tendon lacerations based on the MOI. Further research is necessary to determine whether we should consider different surgical options based on the MOI.
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25. Lister GD, Kleinert HE, Kutz JE, Atasoy E. Primary flexor tendon repair followed by immediate controlled mobilization. J Hand Surg 1977;2:441– 451. 26. Duran RJ, Houser RG. Controlled passive motion following flexor tendon repair in zone 2 and 3. In: Symposium on tendon surgery in the hand. Philadelphia: Mosby, 1974:105–114. 27. Chesney A, Chauhan A, Kattan A, Farrokhyar F, Thoma A. Systematic review of flexor tendon rehabilitation protocols in zone II of the hand. Plast Reconstr Surg 2011;127:1583–1592. 28. May EJ, Silfverskiold KL, Sollerman CJ. Controlled mobilization after flexor tendon repair in zone II: a prospective comparison of three methods. J Hand Surg 1992;17A:942–952. 29. Hwang MD, Pettrone S, Trumble TE. Work of flexion related to different suture materials after flexor digitorum profundus and flexor digitorum superficialis tendon repair in zone II: a biomechanical study. J Hand Surg 2009;34A:700 –704.
30. Hoffmann GL, Buchler U, Vogelin E. Clinical results of flexor tendon repair in zone II using a six-strand double-loop technique compared with a two-strand technique. J Hand Surg 2008;33E:418 – 423. 31. Winters SC, Gelberman RH, Woo SL, Chan SS, Grewal R, Seiler JG III. The effects of multiple-strand suture methods on the strength and excursion of repaired intrasynovial flexor tendons: a biomechanical study in dogs. J Hand Surg 1998;23A:97–104. 32. Zhao C, Amadio PC, Zobitz ME, An KN. Resection of the flexor digitorum superficialis reduces gliding resistance after zone II flexor digitorum profundus repair in vitro. J Hand Surg 2002;27A:316 – 321. 33. Tang JB. Flexor tendon repair in zone 2C. J Hand Surg 1994;19B:72–75. 34. Hogan MV, Bagayoko N, James R, Starnes T, Katz A, Chhabra AB. Tissue engineering solutions for tendon repair. J Am Acad Orthop Surg 2011;19:134 –142.
JHS 䉬 Vol A, December
Clinical Outcomes of Zone II Flexor Tendon Repair Depending on Mechanism of Injury Trevor Starnes, MD, PhD, Rebecca J. Saunders, BSPT, Kenneth R. Means, Jr, MD
Purpose To determine whether mechanism of injury affects outcomes of Zone II flexor tendon repairs. Methods We retrospectively analyzed patients who underwent Zone II flexor tendon repair between 2001 and 2010 with a minimum of 12-month follow-up. Exclusion criteria included fingers with fracture, pulley reconstruction, or flexor tendon bowstringing. The saw group injuries were from saws or from tearing mechanisms; the sharp group had clean transection injuries from knives or glass. At final evaluation, primary outcomes were total passive motion (TPM) and total active motion (TAM) at the proximal interphalangeal and distal interphalangeal joints. Secondary comparisons included strength, Disabilities of the Shoulder, Arm, and Hand (DASH) score, percentage of postoperative tendon rupture, and percentage of patients requiring secondary surgery. The saw group had 13 patients with 17 fingers studied. The sharp group had 21 patients with 24 fingers studied. All patients had primary flexor digitorum profundus repairs in Zone II. Operative records review confirmed for all but 1 patient that flexor digitorum profundus injuries were repaired with a minimum of a 4-strand core suture technique. In the saw group, 9 of 14 fingers with a 50% or greater laceration of flexor digitorum superficialis were repaired; in the sharp group, 15 of 18 such flexor digitorum superficialis injuries were repaired. Average follow-up was 4 years (range, 1–9 y). Results The saw group had significantly less TAM and TPM compared with the sharp group. There was no significant difference in DASH scores, strength measurements, or tendon rupture rates. The rate of secondary surgery was significantly higher in the saw group. Conclusions Tearing types of injury, such as those caused by saws, led to poorer outcomes for Zone II flexor tendon injuries compared with sharp injuries at an average follow-up of 4 years. Our results can be useful when discussing expected outcomes. Mechanism of injury in Zone II flexor tendon lacerations may eventually help define optimal treatment. (J Hand Surg 2012;37A:2532–2540. Copyright © 2012 by the American Society for Surgery of the Hand. All rights reserved.) Type of study/level of evidence Therapeutic III. Key words Outcomes, knife, saw, Zone II flexor tendon repair.
From The Curtis National Hand Center, MedStar Union Memorial Hospital, Baltimore, Maryland. Received for publication September 6, 2011; accepted in revised form September 18, 2012. The authors thank E.F. Shaw Wilgis, MD, for his expertise and mentorship, Lorraine Zellers for serving as research coordinator, Norman Dubin for assistance in statistical analysis, and Anne Mattson for editorial assistance. This study was supported by a grant from The Raymond M. Curtis Research Foundation, The Curtis National Hand Center, Baltimore, Maryland.
2532 䉬 © ASSH 䉬 Published by Elsevier, Inc. All rights reserved.
No benefits in any form have been received or will be received related directly or indirectly to the subject of this article. Corresponding author: Kenneth R. Means Jr, MD, care of Anne Mattson, The Curtis National Hand Center,MedStarUnionMemorialHospital,3333NorthCalvertStreet,JPBM60,Baltimore,MD21218; e-mail: [email protected]. 0363-5023/12/37A12-0013$36.00/0 http://dx.doi.org/10.1016/j.jhsa.2012.09.021
ZONE II FLEXOR TENDONS AND INJURY MECHANISM
especially in Zone II, continues to be a problem with imperfect solutions. Improved surgical repair techniques and rehabilitation protocols have had a positive impact on the outcomes in this patient population.1–5 It is generally accepted that Zone II flexor tendon repairs demonstrate inferior outcomes compared with repairs in other zones.6 –9 Factors that have been shown to play a role in outcomes of flexor tendon repair include associated fracture,1 concomitant nerve injury,10,11 multiple digit injuries, postoperative therapy protocol,12 and a history of smoking.12 We were interested in comparing Zone II flexor tendon repair outcomes based primarily on mechanism of injury (MOI). Historically, investigators have combined multiple MOIs to make generalizations regarding the outcomes for Zone II flexor tendon repair.7,8,13–17 At the 1967 American Society for Surgery of the Hand (ASSH) meeting, Kleinert et al18 reported on primary repair of lacerated flexor tendons in “no man’s land.” A subsequent paper by the group in 197319 summarized their results and techniques. In that landmark paper, the authors stated that “The superior function obtained in repair of sharply incised tendons as opposed to crushing injuries is a well-known fact.”19 Although this statement was no doubt based on a collective vast experience at the time, no direct references or comparative study characteristics based on MOI were listed. Although most surgeons would likely agree with this statement, studies that examine the influence of MOI on outcome for Zone II flexor tendon repairs are limited. The purpose of this study is to determine whether the MOI has an effect on outcomes of Zone II flexor tendon repairs at least 1 year after injury.
F
LEXOR TENDON REPAIR,
METHODS Inclusion and exclusion criteria We completed a retrospective cohort study using data from the medical records of patients who underwent Zone II flexor tendon repair between January 2001 and May 2010 at our institution with at least a 12-month follow-up. Institutional review board approval was granted before we reviewed medical records and contacted patients. Potential subjects were identified by search of Current Procedural Terminology code 26356 from institutional billing records. Only patients who had repair of flexor tendon lacerations in Zone II of the fingers were included. Eight fellowship-trained attending hand surgeons performed the repairs. Surgeons preserved as much of the flexor pulley system as possible but maintained a sufficient amount of the A2 and A4 pulleys, typically at least 50% in our practice, to prevent
2533
flexor tendon bowstringing and allow postoperative rehabilitation.20,21 Exclusion criteria included patients younger than 18 and older than 75 years, fingers with concomitant fractures, and fingers that required pulley reconstruction or had evidence of flexor tendon bowstringing at the end of the operative procedure. A final evaluation of included patients was completed by a single Certified Hand Therapist who performed all range of motion and strength measurements. From the medical record, we gathered the MOI and surgical treatments provided and confirmed this information at follow-up clinical evaluation. All patients had postoperative hand therapy with various early motion protocols for the digits that were included in the study. Range of motion Following American Medical Association guidelines, the therapist measured active and passive range of motion and flexion contractures for each injured digit at the proximal interphalangeal (PIP) and distal interphalangeal (DIP) joints using a goniometer.22 We calculated total active motion (TAM) and total passive motion (TPM) according to Strickland and Glogovac’s criteria.23 We completed a power analysis before the study and determined that 26 observations per group would give an 80% chance of detecting a clinically relevant 20° difference between the injury groups at the .05 significance level, assuming an SD of 25°.12 Grip and pinch strength The hand therapist measured grip strength using a dynamometer (Jamar; Sammons Preston Rolyan, Bolingbrook, IL) set in position 2. The patient was seated with the elbow joint flexed at 90° and the forearm in the neutral position. The patient’s wrist was maintained between 0° and 30° of extension and 0° and 15° ulnar deviation. The hand therapist asked the patient to grasp the dynamometer with maximal effort for 3 seconds and recorded the average of 3 measurements. The hand therapist performed the lateral pinch strength measurement using a pinch gauge (B&L Engineering, Tustin, CA). The patient was positioned identically as for the grip measurements. The therapist asked the patient to pinch the gauge between her or his thumb pad and the lateral aspect of the index finger middle phalanx with maximal effort for 3 seconds and recorded the average of 3 measurements. Outcome questionnaires We administered the Disability of the Arm, Shoulder and Hand (DASH) outcome questionnaire to each par-
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FIGURE 1: Algorithm results for determining the 2 patient cohorts. CPT, Current Procedural Terminology; FPL, flexor pollicis longus; MOI, mechanism of injury; NHS, National Hand Specialists.
ticipant and scored according to the instructions provided by the Institute for Work and Health (© 2006).24 The hand therapist also obtained a standardized 10point visual analog scale (VAS) score for pain from patients. Statistical analysis We compared demographic data using a chi-square analysis. We performed injured digit analysis, surgical intervention, and complication analysis with the Fisher exact test. We analyzed range of motion, strength, DASH, and VAS data by a t-test, assuming equal variances. We completed a multifactor analysis of variance to determine the relationship between flexor digitorum profundus (FDP)-only repairs and FDP and flexor digitorum superficialis (FDS) repair and TAM outcome. Demographics Our Current Procedural Terminology code search yielded 504 patient records with documented complete laceration of the FDP in Zone II. We reviewed each operative note and excluded 260 patients secondary to concomitant fracture in the injured digit. We excluded 41 patients with flexor pollicis longus tendon repair. We separated the remaining cohort of 203 patients into 2 groups based on MOI (Fig. 1).
The saw group (54 patients) had sawing or tearing MOIs including saw, lathe, fan, and crush mechanisms. The sharp group (149 patients) had clean transection MOIs occurring from knives, glass, metal, and broken porcelain. We attempted to contact the 54 patients in the saw group and a random sample of 104 patients in the sharp group. Thirteen patients (17 fingers) in the saw group and 21 patients (24 fingers) in the sharp group returned for clinical evaluation. The saw group patients had 11 saw injuries, 1 lathe injury, and 1 fan injury. The sharp group patients had 15 knife injuries and 6 glass lacerations. Table 1 presents demographic data for both groups. All patients underwent primary repair of the FDP injury in Zone II. Table 2 presents FDP repair details and associated injuries/surgical interventions in both groups. We did not analyze whether surgeon, FDP repair type, number of FDP core suture strands, type of core suture used, use of an epitendinous suture, and/or associated pulley repair were independent factors with regard to range of motion outcomes because of the significant amount of variation for some categories and limited variation in other categories. One patient’s operative note from the saw group had incomplete information with regard to repair technique. All other patients had documentation of at least a 4-strand core suture repair of
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ZONE II FLEXOR TENDONS AND INJURY MECHANISM
TABLE 1.
Demographic Data
TABLE 3. Fingers Involved
Saw Group
Sharp Group
Male:female
13:0
14:7
Mean age (y)
47 ⫾ 4
Hand dominance (R:L:A)
11:1:1
High school
5
7
Vocational training
4
College degree
2
Graduate degree
2
2
P
2 (12)
0 (0)
.17
42 ⫾ 3
.30
Dominant middle finger
1 (6)
1 (4)
.99
19:2:0
NS
Dominant ring finger
2 (12)
4 (17)
.99
.82
Dominant small finger
1 (6)
8 (33)
.06
Nondominant index finger
3 (18)
6 (25)
.71
6
Nondominant middle finger
4 (24)
0 (0)
.02
6
Nondominant ring finger
2 (12)
3 (13)
.99
Nondominant small finger
2 (12)
2 (8)
.99
.13
Unskilled manual
0
1
Skilled manual
8
5
Nonmanual/office work
0
2
Professional/management
5
13
Workers comp (Y:N)
2:11
6:15
.44
Tobacco use (Y:N)
2:11
6:15
.38
A, ambidextrous; L, left; NS, not significant; R, right. Bold indicates significant difference (P ⬍ .05).
Injury and Surgical Repairs
FDS repaired
Saw Group (%)
Sharp Group (%)
P
14/17 (82)
18/24 (75)
.99
9/14 (64)
15/18 (83)
.25
Cruciate tendon repair
10/17 (59)
18/24 (75)
.32
Nerve repair
13/17 (77)
10/24 (42)
.03
6/17 (35)
1/24 (4)
13/17 (77)
2/24 (8)
Vascular repair Other injured digits
P
Dominant index finger
Occupation
FDS cut ⱖ 50%
Sharp Group (%)
.02
Education
TABLE 2.
Saw Group (%)
.01 < .001
FDS, flexor digitorum superficialis. Bold indicates significant difference (P ⬍ .05).
each FDP tendon. Of these patients, all except 3 in the saw group also had an epitendinous suture placed in the FDP tendon. In the saw group, there were 10 cruciate, 4 Strickland, and 2 modifiedKessler looped-suture repairs. In the sharp group, there were 18 cruciate, 3 Strickland, and 1 modified-Kessler looped-suture repairs. The major repair type was cruciate for both injury groups, with 59% in the saw group and 75% in the sharp group (P ⫽ .32). One patient in the saw group had repair of the A4 pulley. No other pulley repairs were performed. We did not observe clinically notewor-
Bold indicates significant difference (P ⬍ .05).
thy bowstringing of the finger flexor system for any patients intraoperatively or after surgery. Follow-up averaged 4.7 years ⫾ 0.6 years (range, 1.6 – 8.4) in the saw group and 3.9 years ⫾ 0.5 years (range, 1.0 – 8.6) in the sharp group, which was not a significant difference (P ⫽ .36). Injured digits (Table 3) were similar between the groups except for a statistically significantly increased number of nondominant middle finger injuries in the saw group (P ⫽ .02). There were 25 patients confirmed as having early active flexor tendon protocols (74% [25/34] overall, 81% [17/21] in the sharp group, and 62% [8/13] in the saw group; P ⫽ .25). One patient in each group initially had early modified Duran protocol consisting of passive flexion only for the first 3 weeks (6% [2/34] overall, 5% [1/21] in the sharp group, and 8% [1/13] in the saw group; P ⫽ .99). Three patients in the saw group had early hand therapy, but we could not confirm the exact protocol used (23% [3/13]; P ⫽ .05 compared with the sharp group). There were 2 patients in each group for whom we could not locate initial therapy charts or prescriptions (12% overall [4/34], 10% [(2/21] in the sharp group, and 15% [2/13] in the saw group; P ⫽ .63). RESULTS The TAM for the saw group was significantly worse than that for the sharp group (86° ⫾ 14° vs 114° ⫾ 7°; P ⫽ .05). We compared the percentage of normal TAM between the saw group and the sharp group. Using Strickland and Glogovac’s classification23 of TAM outcomes criteria, we also compared the percentage of excellent, good, fair, and poor results for both groups (Table 4). The saw group fingers also had a statistically
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TABLE 4.
ZONE II FLEXOR TENDONS AND INJURY MECHANISM
Total Active Motion Outcomes Normal TAM (%)
Strickland and Glogovac Excellent (%)
Strickland and Glogovac Good (%)
Strickland and Glogovac Fair (%)
Strickland and Glogovac Poor (%)
Saw group
49 ⫾ 8
3 (18)
2 (12)
3 (18)
9 (53)
Sharp group
65 ⫾ 4
5 (21)
6 (25)
8 (33)
5 (21)
P
.05
.03
.03
TAM ⫽ (active PIP flexion ⫹ active DIP flexion) – (flexion contracture at PIP ⫹ DIP). TPM ⫽ (passive PIP flexion ⫹ passive DIP flexion) – (flexion contracture at PIP ⫹ DIP). Percentage of normal TAM ⫽ TAM/175° ⫻ 100. Bold indicates significant difference (P ⬍ .05).
significantly worse average TPM at the PIP and DIP joints than patients in the sharp group (Fig. 2). There were larger flexion contractures for the combined PIP and DIP joints in the saw group compared with the sharp group, which was also significant (Fig. 2). Table 5 reports the lateral pinch, grip strength, DASH, and VAS pain scores for both groups, for which there were no significant differences other than for uninjured hand grip strength, which was stronger in the saw group. Tendon rupture occurred in 1 of 17 digits in the saw group. No tendon ruptures occurred in the sharp group’s digits (P ⫽ .4). However, a significantly different rate of secondary surgery was evident with the saw group digits requiring secondary surgery in 9 of 17 digits compared with 3 of 24 digits in the sharp group (P ⫽ .01). Secondary surgeries in the saw group included PIP joint arthrodesis in the patient with a postoperative tendon rupture, a cross-finger flap division, tenolysis in 4 digits, and tenolysis and capsulectomy in 3 digits. Secondary surgeries in the sharp group included tenolysis in 2 digits and application of a Digit Widget (Hand Biomechanics Lab, Inc., Sacramento, CA) for flexion contracture in 1 digit. We completed a regression analysis to determine whether FDP-only repair and combined FDP and FDS repair were independent factors with regard to TAM in patients with both tendons cut. We did not have enough power to determine whether the TAM differences we observed favoring repair of both FDP and FDS for the saw group and the sharp group were significant (Fig. 3). DISCUSSION Ever since Kleinert et al18 reported on primary repair of Zone II flexor tendon lacerations in 1967 at the annual ASSH meeting, surgical repair and research have evolved to focus on completing the strongest biomechanical construct with the best patient outcomes. Zone II flexor tendon outcome studies review the techniques of repair within the tendon sheath and emphasize the
importance of meticulous tendon handling techniques. Multiple studies have also focused on postoperative therapy protocols that have advanced from immobilization to early passive flexion motion protocols such as the Kleinert et al25 or Duran and Houser26 protocols to, more recently, early active flexion therapies.12 Multiple Zone II flexor tendon outcome studies have combined various MOIs. Outcomes are worse with concomitant fracture,1 nerve injury,11 and contaminated wounds.1 Kleinert et al19 stated that crush injuries do worse than sharp lacerations. For our study, we attempted to compare Zone II flexor tendon repair outcomes based primarily on MOI. Our study results led us to reject our null hypothesis regarding MOI in relation to range of motion. We have shown inferior outcomes for injuries that occur by a tearing mechanism such as a saw or lathe. There was significantly less TPM and TAM as well as a larger flexion contracture at 4.7 years follow-up in the saw group. These differences may be because of an increase in the severity of injury with a tearing mechanism as compared with a clean transection injury as shown in Table 2. Several potential issues can limit the strength of our conclusions. At our institution, digits with Zone II flexor tendon repair and concomitant digital nerve repair are not rehabilitated any differently from those that do not have nerve injuries. However, the nerve injury itself may be an independent factor for a worse range of motion outcome. Many of our patients were transported to our facility from a considerable distance for their initial surgery and, therefore, did the majority of their therapy at a location closer to their home. The type of postoperative therapy protocol itself could not be included in our analysis of independent factors affecting range of motion but is known to have an effect on overall outcome.12,27,28 The presence of associated injuries in other digits may also have led to slower reha-
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ZONE II FLEXOR TENDONS AND INJURY MECHANISM
180 160 140 D e 120 g 100 r 80 e e 60 s 40
159.8
P = .02
133.8 Saw Group Sharp Group
20 0 A
Total Passive Moon
140 120 D 100 e g 80 r e 60 e 40 s
P = .05 114.3 86.2
Saw Group Sharp Group
20 0 B
Total Acve Moon
50 45 D e g r e e s
40
P = .005
35 30
39.7
25
Saw Group
20
Sharp Group
15 10
17.2
5 0 C
Flexion Contracture
FIGURE 2: A Average total passive motion (TPM), B total active motion (TAM), and C flexion contracture results and 95% confidence intervals for the Saw Group (saw/tearing injury mechanism) compared with the Sharp Group (sharp injury mechanism).
bilitation protocols or just to poorer outcomes owing to greater overall trauma to the injured hand. Because of the low number of observations in these subgroups, we cannot rule out the possibility that negative findings may be the result of Type II errors. In fact, it may even be likely that the poorer outcomes in the saw group are caused by the greater number of same-digit and other-digit injuries in the same hand. We
also had a relatively large number of surgeons performing different flexor tendon repair techniques with different suture materials. There is limited comparative information about flexor tendon repair techniques and suture material impact on range of motion outcomes. Hwang et al29 performed a biomechanical study and found that suture material did not affect work of flexion whereas repair of both FDP and FDS compared with
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2538
TABLE 5.
ZONE II FLEXOR TENDONS AND INJURY MECHANISM
Strength, DASH, and Pain Outcomes Injured Hand Grip (kg)
Uninjured Hand Grip (kg)
% Uninjured Grip (%)
Injured Hand Lateral Pinch (kg)
Uninjured Hand Lateral Pinch (kg)
% Uninjured Lateral Pinch (%)
DASH
VAS Pain
Saw group
37 ⫾ 3
47 ⫾ 2
84 ⫾ 5
11.0 ⫾ 0.7
11.0 ⫾ 0.6
99 ⫾ 6
16 ⫾ 4
0.9 ⫾ 0.3
Sharp group
34 ⫾ 3
38 ⫾ 2
88 ⫾ 5
9.0 ⫾ 0.5
10.0 ⫾ 0.4
93 ⫾ 3
12 ⫾ 3
1.0 ⫾ 0.4
.3
.03
.59
.06
.07
.37
.47
.83
P
DASH, Disability of the Arm, Shoulder and Hand; VAS, visual analog score. Bold indicates significant difference (P ⬍ .05).
Interaction Plot 140.0
Total Active Motion
120.0 P = .07
100.0 80.0
Saw Sharp
60.0 40.0 20.0 0.0
FDP
FDP+FDS
FIGURE 3: Interaction plot comparing total active motion (TAM) for flexus digitorum profundus (FDP) only versus FDP and flexor digitorum superficialis (FDS) repair for the 2 groups.
FDP repair alone did increase work of flexion. Hoffman et al30 found that Zone II FDP repair with a 6-strand core suture, compared to 2-strand core suture repair, was associated with better range of motion and strength and fewer complications at relatively early 8- to 17week follow-up. In a dog study, Winters et al31 found that 4 different suture techniques did not affect joint range of motion at 3 and 6 weeks after surgery but the 8-strand technique led to a stronger tendon repair than other techniques. Because all of our patients had at least a 4-strand core suture repair of the FDP tendon injury and there was only 1 postoperative flexor tendon rupture, we believe the differences in repair technique are not clinically meaningful. However, we did not design the study to evaluate
repair technique as an independent variable for range of motion outcome, which is another potential weakness of our study. For the 1 patient with incomplete intraoperative documentation about repair technique, we did not observe postoperative flexor tendon rupture. There is controversy regarding repair of both FDP and FDS or just FDP in Zone II flexor tendon lacerations. Previous biomechanical studies have demonstrated that partial or complete FDS excision decreases gliding resistance in Zone II flexor tendon repair.32 Tang33 has also demonstrated this clinically with a nonsignificant trend toward increased TAM in patients in which only the FDP was repaired. However, others have suggested the importance of maintaining at least
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ZONE II FLEXOR TENDONS AND INJURY MECHANISM
part of the FDS as a gliding bed for the FDP repair to decrease the work of flexion29 or to increase active PIP joint flexion excursion and power. Our study suggests that further research is necessary to define outcomes of FDP repair with or without FDS repair for these types of injuries. Our impression has been that tearing-type injuries, such as those seen from power saws, do worse than clean/sharp tendon injuries even when fractures, nerve injuries, or other digit injuries are not present. For digits with power saw injuries, we may vein graft injured vessels, graft or use synthetic conduits for nerve injuries, and even graft or perform local flaps for soft tissue coverage, yet we typically repair the flexor tendon injuries primarily if the débrided tendon ends can be approximated without excessive tension or digital flexion. This consideration could even be taken to the next level for digits that have bone injury or that are complete replantations. We sought to first determine whether our experience and the literature reports about the poorer outcomes for Zone II flexor tendon repair with these types of injuries are correct. We believe our current study has confirmed this impression at our institution. We tried to eliminate variables, such as fracture and replantation, that would alter our typical postoperative therapy protocol for Zone II flexor tendon repairs. Perhaps consideration of different treatment options, such as delayed tendon grafting as was classically done for all Zone II injuries, is warranted for these injuries or even more severe injuries such as those with fractures, revascularization, or replantation. Some of our most experienced partners believe that the positive results for Zone II repairs reported first by Kleinert and then by many others since have been used to excessively generalize recommendations for primary repair in all or most traumatic cases, regardless of MOI, need for replantation/revascularization, or presence of associated injuries. As a possible practice application, MOI should be considered as another potential factor in outcomes for Zone II flexor injuries. Further study may also involve incorporation of tendon bioengineering principles such as scaffolds, stem cells, or growth factors at the site of injury and repair,2,34 which may lead to improved range of motion, tendon repair strength, and restoration of native tendon tissue regardless of MOI. This study serves as a prognostic guide for patients with these types of injury. It will help guide the surgeon in providing expected outcomes to patients who sustain Zone II flexor tendon lacerations based on the MOI. Further research is necessary to determine whether we should consider different surgical options based on the MOI.
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