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Schultz metacarpophalangeal arthroplasty: A long-term follow-up study
Schultz metacarpophalangeal arthroplasty: A long-term follow-up study We describe a prospective, long-term evaluation of the Schultz metacarpophalangeal joint implant. The prosthesis is a semiconstrained, cemented implant with a ball-in-socket articulation. Thirty-six implants were followed for an average of 10.9 years. There was a progressive decrease in range of motion and strength and a recurrence of ulnar deviation. The neck of the proximal phalangeal component fractured in 39% of the joints. Periarticular heterotopic bone formed in all joints, but was extensive in only 22%. Although some lucency of the bone-cement interface was seen in 80 % of the joints, no prosthetic loosening occurred in this series. Our results indicate that long-term, intramedullary cement fixation of relatively long-stemmed components can be satisfactory. However, the articulated portion of this implant does not consistently withstand the stresses transmitted across the joint and does not provide long-term joint stability. (J HAND SURG 1990;15A:641-5.)
Brian D. Adams, MD, Little Rock, Ark., William F. Blair, MD, and Donald G. Shurr, CO, LPT, Iowa City, Iowa
Metacarpophalangeal eMP) arthroplasty has been used extensively during the last few decades for the treatment of rheumatoid arthritis. To provide a more stable joint with greater motion and digital strength, several "total" MP joint prostheses have been designed. 1·3 Although these prostheses have not proved to be clinically successful, I, 4. 5 long-term studies providing an explanation for their failure have not been published. The Schultz prothesis is a semiconstrained device made of a metal phalangeal component and a plastic metacarpal component with a ball-in-socket articulation, The components are fixed in the medullary canals by bone cement. This article describes a longterm prospective evaluation of this prosthesis, with emphasis on the unique features of the arthroplasty.
From the Department of Orthopedic Surgery, University of Iowa Hospitals and Clinics, Iowa City, Iowa. Received for publication April 13, 1989; accepted in revised form July 27, 1989. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. Reprint requests: Brian D. Adams, MD, Department of Orthopedic Surgery, University of Arkansas for Medical Sciences, Little Rock, AR 72205.
3/1116131
Materials and methods Eight patients with rheumatoid arthritis (6 women and 2 men) had 36 Schultz prosthetic MP joint replacements in 9 hands at the University of Iowa between 1974 and 1976. All patients had the dominant hand operated on (6 right, 3 left); one patient had bilateral operations, Average age at the time of operation was 47 years (range, 28 to 66 years). All patients had been placed in a prospective clinical protocol at the time the operation was planned, A preoperative evaluation and 3-year and 5-year interim evaluations were done, One patient died 6.5 years after operation. The remaining patients returned for a final evaluation. The average follow-up period was 10.9 years (range, 5 to 12 years). Physical examination included an assessment of joint motion and finger deformity. Functional testing included key pinch and grip strength measurements. Patient satisfaction concerning appearance, function, and pain relief was recorded. Complete records and radiographs were available for all patients at each followup. The indications for the Schultz arthroplasty were gross joint destruction and deformity. Technique Since the surgical technique has been described in detail previously," only the major technical aspects of the procedure will be reviewed. The joints are entered
THE JOURNAL OF HAND SURGERY
641
The Journal of 642
HAND SURGERY
Adams, Blair, and Shurr
AVERAGE MP JOINT ARC OF MOTION ALL FINGERS 40
30 (I)
w
w
~ w o
20
10
o PREOPERATIVE
3 YEARS
5 YEARS
FINAL
Fig. 1. A gradual decrease in average MP joint motion during the follow-up period is shown.
on one side of the extensor tendon and a synovectomy is done. Careful preparation of the metacarpal head is required for proper fit of the prosthesis. The inferior and lateral cortices are cut to the length of the prosthetic head and the superior ledge is retained. The articular surface of the proximal phalanx is removed. A trial reduction of the two components is done to assess the need for soft tissue release. However, if possible, the collateral ligaments should be retained. Bone cement is inserted into each canal and the components are inserted. The prosthesis is articulated by a snap fit. Wound closure is standard. Schultz was present to provide instruction during the implanting of the first 20 prostheses. The original prosthetic design was used in all fingers. A metallic hinge prosthesis of the Flatt design was inserted in 12 ipsilateral proximal interphalangeal (PIP) joints during the same operation. Results
The results of 36 Schultz MP joint replacements, with an average follow-up of 10.9 years were reviewed. Since a metallic hinge prosthesis had been inserted in one third of the PIP joints, an evaluation of the PIP joint was not included. Before operation, the average active range of motion (AROM) of all MP joints was 31 degrees, with an average arc of motion from 64 degrees extension to 95 degrees flexion. At the 3-year
follow-up, the AROM was 32 degrees, with an arc from 40 degrees to 72 degrees. At the 5-year follow-up, the AROM was 23 degrees, with an arc from 46 degrees to 69 degrees. At the final follow-up, the AROM was 10 degrees, with an arc from 58 degrees to 68 degrees. The progressive decrease in AROM of all MP joints is shown graphically in Fig. 1. There was a gradual recurrence toward a more flexed position. Ulnar deviation recurred in all digits. The average deviation was 32 degrees before operation, 15 degrees at 3 years, 20 degrees at 5 years, and 28 degrees at final follow-up. The degree of deviation was greater in fingers with broken implants. Extensor tendon dislocation recurred in the 27 fingers with recurrent ulnar deviation greater than 20 degrees. Palmar subluxation recurred only in the fingers with a fractured prosthesis (14 fingers). Average preoperative key pinch was 3.2 kg and grip strength was 8.8 kg. The 3-year and 5-year measurements showed a gradual decline, with final measurements of 1.9 kg and 2.9 kg, respectively. The patients judged their appearance and function to be improved in four cases, to be the same in one, and made worse in three. Radiographs showed a fracture through the neck of the metal proximal phalangeal component in 39% of the prostheses (Fig. 2). Fractures involved 5 index, 4 long, 3 ring, and 2 small fingers. Periarticular het-
Vol. 15A, No.4 July 1990
Fig. 2. Fracture of the neck-stem junction of the metallic proximal phalangeal component has occurred in all four fingers, with recurrence of ulnar drift; no component loosening.
erotopic bone formation occurred in all hands (Fig. 3). However, this was extensive in only 22%. A lucency of the bone-cement interface measuring Lto 3 mm was seen about the proximal (juxta-articular) 4 mm of the phalangeal component in 80%. This was always associated with a thickening or expansion of the cortex, but was less if there was component fracture. A similar, but less prominent change was seen about the distal (juxta-articular) portion of the metacarpal component in 36%. A complete 1 mm lucency of the bone-cement interface occurred about the stem of five phalangeal components. However, in all five fingers a PIP joint implant shared the same medullary canal, which made evaluation of changes difficult. A correlation of function and prosthetic fracture was done. Since all fractures had occurred within 5 years, the 3-year values were used for the analysis. The results show that a fracture did not occur if the MP joint had more than 25 degrees of AROM. Patients with greater than 6.4 kg grip strength or 5.5 kg pinch strength fractured at least one implant. However, one patient who had only 2.7 kg grip strength and 1.4 kg pinch strength fractured two implants.
Schultz MP arthroplasty
643
Fig. 3. Periarticular heterotopic bone formation is seen in all four fingers. Lucency of the bone-cement interface is present about the juxta-articular portion of the components. Index and long finger components have fractured; no component loosening.
Six of the 12 PIP joint implants that were inserted concurrently with a Schultz prosthesis were removed because of infection. To erradicate the infection in three of these six fingers, removal of a Schultz prosthesis from one finger and amputation of two fingers was required. In only one finger was a Schultz prosthesis removed because of infection unrelated to a PIP joint implant infection. This occurred in a woman who sustained a deep dorsal abrasion that exposed the joint. There was no evidence of hematogenous seeding as a cause of infection in this study group. Discussion A method for MP arthroplasty in the patient with rheumatoid arthritis that provides a satisfactory longterm result continues to elude hand surgeons. Although arthroplasty employing a silicone implant is widely used, the implant is not a true prosthesis and does not restore full motion or significantly improve strength. 6 In addition, problems with component fracture and recurrence of deformity are common. Physicians and engineers have attempted to design a prosthesis that duplicates the mechanics of the normal MP joint.
644
The Journal of HAND SURGERY
Adams, Blair, and Shurr
However, the design requirements are complex and demending." 7.8 These requirements have been analyzed in mathematical and laboratory models to quantitate the normal articular anatomy and joint forces.": 9. 10 Unfortunately, current mathematical models make many assumptions and have significant limitations.'! Schultz and colleagues" developed an experimental device that made direct measurements of the MP joint in three dimensions. The data was used to construct a computersimulated model of the MP joint. They claimed the collateral ligaments are taut in all positions of the flexion-extension arc and the MP joint moves with a changing axis of rotation. 2.12 Schultz applied these ideas in designing the prosthesis analyzed in this study. Gillespie'? performed a biomechanical evaluation of several MP joint implants including the Schultz prosthesis. The range of motion of the Schultz implant was neutral to 90 degrees of flexion, with an 8 degree arc of radial-ulnar deviation in extension, and no deviation in full flexion. The axis of rotation during flexionextension varied in an unpredictable manner and fingertip force measurements were inconsistent. The authors concluded that the variability in fingertip force was due to the unpredictable changing center of rotation. Therefore, the implant did not function according to the objective of the design in their study. In addition, cold flow deformation was seen in the articulated portion of the plastic metacarpal component. Rheumatoid arthritis causes an ulnar and palmar displacement of the force nucleus described by Zancolli. 14 Thus both static and dynamic forces are altered. To increase stability, the Schultz prosthesis is designed to retain the collateral ligaments. Unfortunately, this is possible only when resection of the proximal phalanx is minimal. The ball-in-socket design is intended to dampen the forces acting across the joint, thus decreasing the stress transmitted to bone. However, plastic deformation of the slot in the metacarpal component and fracture of the metallic neck of the phalangeal component contributed to recurrence of deformity. It appears the forces generated by routine use of the hand were greater than the prosthetic tolerances. An interesting finding in this study was the lack of component loosening. Although limited juxta-articular lucency of the bone-cement interface was seen in the majority of fingers, no frank loosening occurred. Therefore, the design of the Schultz prosthesis appears to be satisfactory for fixation in the medullary canals. However, long-term stable fixation appears to increase stresses in the articulated portion of the implant leading to frequent materials failure. Periarticular heterotopic bone formation is a common finding with all methods
of MP arthroplasty, but was more prominent in this study. The cause of the heterotopic bone is not clear. The bone formation often extends from a cut edge and follows the course of the retained collateral ligaments. This study is the longest reported follow-up of a cemented articulated MP joint prosthesis. The results indicate that long-term intramedullary cement fixation of relatively long-stemmed components can be satisfactory. However, the articulated portion of this implant does not consistently withstand the stresses transmitted across the joint and does not provide long-term stability. Clinical results measured in this study are similar to the results reported for silicone implants." 15 Although silicone implants continue to be widely used, their design does not provide an ideal biomechanical reconstruction of the MP joint. Further research and development is needed to design a better prosthesis that is both biologically and mechanically suited to the rheumatoid MP joint.
1.
2.
3.
4.
5.
6.
7.
8. 9.
10.
REFERENCES Flatt AB. Care of the arthritic hand. 4th ed. St Louis: The CV Mosby Co., 1983. SchultzRJ. Total metacarpophalangeal joint arthroplasty with limited metacarpal head resection. In: Inghs AE, ed. Symposium on total joint replacement of the upper extremity. American Academy Orthopedic Surgeons. St Louis: The CV Mosby Co., 1982:199-216. Steffee A. History, design and development of Steffee metacarpophalangeal prosthesis. In: Inghs AB, ed. Symposium on total joint replacementof the upper extremity. AmericanAcademy Orthopedic Surgeons. St Louis: The CV Mosby Co., 1982:179-86. Steffee AD, Beckenbaugh RD, Linscheid RL, Dobyns JH. The development, technique, and early clinical results of total joint replacementfor the metacarpophalangeal joint of the fingers. Orthopaedics 1981;4:175-80. Linscheid RL, Beckenbaugh RD, Dobyns JH, Cooney WP.Metacarpophalangeal arthroplasty withSteffee prostheses. In: Inghs AE, ed, Symposium on total joint replacement of the upper extremity. American Academy Orthopedic Surgeons. St Louis: The CV Mosby Co., 1982:187-98. Blair WF, Shurr DO, BuckwalterJA. Metacarpophalangeal joint implant arthroplasty with a silastic spacer. J Bone Joint Surg 1984;66A:365-70. Flatt AB, Fischer OW. Biomechanicalfactors in the replacement of rheumatoid finger joints. Ann Rheum Dis 1969;28(suppl):36-44. Neale MJ. Theoretical design of various types of finger joint. Ann Rheum Dis 1969;28(suppl):25-30. Smith EM, Juvinall RC, Bender LF, Pearson JR. Role of finger flexors in rheumatoid deformities of the metacarpophalangeal joints. Arthritis Rheum 1964;7:467-80. Flatt AB. The pathomechanics of ulnar drift: a biome-
Vol. 15A, No.4 July 1990
chanical and clinical study. Social and Rehabilitation Services, grant no. RD 2226M, 1971. 11. Linscheid RL, Chao EY. Biomechanical assessment of finger function in prosthetic joint design. Orthop Clin North Am 1973;4:317-30. 12. Schultz RJ, Storace A. A new viewpoint on metacarpophalangeal joint motion and the role of the collateral ligaments. J HAND SURG 1978;3:291. 13. Gillespie TE, Flatt AB, Youm Y, Sprague BL. Blome-
Schultz MP arthroplasty
chanical evaluation of metacarpophalangeal joint prosthesis designs. J HAND SURG 1979;4:508-21. 14. Zancolli E. Structural and dynamic bases of hand surgery. Philadelphia: JB Lippincott, 1979. 15. Goldner JL, Gould JS, Urbaniak JR, McCollum DE. Metacarpophalangeal joint arthroplasty with siliconeDacron prostheses (Niebauer type): six and a half years experience. J HAND SURG 1977;2:200-11.
A splint for controlled active motion after flexor tendon repair Design, mechanical testing, and preliminary clinical results A splint for controlled active motion after flexor tendon repair is described. It incorporates a single core-coated elastic band passing around a palmar pulley and attached proximally to a spring wire. Its mechanical properties were tested against six other systems. The tension in various systems all rose near full extension. However, the palmar pulley, the spring wire, and the elastic band each could lower the tension significantly. When the bending moments at the interphalangeal joints were measured, all systems produced a peak during the latter part of extension. With the palmar pulley, spring wire, and elastic band, the rise was minimal and in fact, the bending moments diminished near full extension. Initial results in 28 flexor tendon repairs using this splint showed less flexion contracture when compared with 78 flexor tendon repairs using a standard rubber baud anchored at the wrist. (J HAND SURG 1990ilSA:645-Sl,)
S. P. Chow, MS, FRCSE, FACS, M. M. Stephens, MS, FRCSI, W. K. Ngai, FRCSE, Y. C. So, FRCS, FRCSE, FRACS, W. K. Pun, MCh(Orth), FRCSG, FReSE, FRACS, M. Chu, OTR, and C. Crosby, MCSP, Hong Kong
Nowadays there is great emphasis on a meticulous postoperative program following flexor tendon repair. 1-7 The concept of controlled early mobilization that was popularized by Kleinert et al. 8 aimed From the Departments of Orthopaedic Surgery,Occupation Therapy,
and Physiotherapy, University of Hong Kong, Queen Mary Hospital, Hong Kong. Received tor publication March 2, 1989; accepted in revised form Aug. 3, 1989. No benefits in any form have been received or will bereceived from a commercial party related directly or indirectly to the subject of this article. Reprint requests: S. P. Chow, MS, FRCSE, FACS, Department of Orthopaedic Surgery, University of HongKong, Queen MaryHospital, Hong Kong, 5-8192258. 3/1/16645
at protected gliding of the repaired tendon using a special splint, thus minimizing the formation of thick tendon adhesions. However, the rubber band traction system that Kleinert et al. 8 originally used produced a sharp rise in tension at the last 20 to 30 degrees of extension, consequently leading to flexion contracture of the proximal interphalangeal (PIP) joint. Frequently, splintage at 6 to 8 weeks is required to correct this contracture. 9 To overcome this problem, various methods had been devised to produce a more "constant" tension, such as the use of a much longer rubber band anchored at the proximal forearm or the incorporation of a roller wheel system. IO The direction of pull of the original Kleinert rubber band traction system also did not allow full flexion at the distal interphalangeal (DIP) joint, and therefore, did not allow much movement at this joint. As THE JOURNAL OF HAND SURGERY
645
Brian D. Adams, MD, Little Rock, Ark., William F. Blair, MD, and Donald G. Shurr, CO, LPT, Iowa City, Iowa
Metacarpophalangeal eMP) arthroplasty has been used extensively during the last few decades for the treatment of rheumatoid arthritis. To provide a more stable joint with greater motion and digital strength, several "total" MP joint prostheses have been designed. 1·3 Although these prostheses have not proved to be clinically successful, I, 4. 5 long-term studies providing an explanation for their failure have not been published. The Schultz prothesis is a semiconstrained device made of a metal phalangeal component and a plastic metacarpal component with a ball-in-socket articulation, The components are fixed in the medullary canals by bone cement. This article describes a longterm prospective evaluation of this prosthesis, with emphasis on the unique features of the arthroplasty.
From the Department of Orthopedic Surgery, University of Iowa Hospitals and Clinics, Iowa City, Iowa. Received for publication April 13, 1989; accepted in revised form July 27, 1989. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. Reprint requests: Brian D. Adams, MD, Department of Orthopedic Surgery, University of Arkansas for Medical Sciences, Little Rock, AR 72205.
3/1116131
Materials and methods Eight patients with rheumatoid arthritis (6 women and 2 men) had 36 Schultz prosthetic MP joint replacements in 9 hands at the University of Iowa between 1974 and 1976. All patients had the dominant hand operated on (6 right, 3 left); one patient had bilateral operations, Average age at the time of operation was 47 years (range, 28 to 66 years). All patients had been placed in a prospective clinical protocol at the time the operation was planned, A preoperative evaluation and 3-year and 5-year interim evaluations were done, One patient died 6.5 years after operation. The remaining patients returned for a final evaluation. The average follow-up period was 10.9 years (range, 5 to 12 years). Physical examination included an assessment of joint motion and finger deformity. Functional testing included key pinch and grip strength measurements. Patient satisfaction concerning appearance, function, and pain relief was recorded. Complete records and radiographs were available for all patients at each followup. The indications for the Schultz arthroplasty were gross joint destruction and deformity. Technique Since the surgical technique has been described in detail previously," only the major technical aspects of the procedure will be reviewed. The joints are entered
THE JOURNAL OF HAND SURGERY
641
The Journal of 642
HAND SURGERY
Adams, Blair, and Shurr
AVERAGE MP JOINT ARC OF MOTION ALL FINGERS 40
30 (I)
w
w
~ w o
20
10
o PREOPERATIVE
3 YEARS
5 YEARS
FINAL
Fig. 1. A gradual decrease in average MP joint motion during the follow-up period is shown.
on one side of the extensor tendon and a synovectomy is done. Careful preparation of the metacarpal head is required for proper fit of the prosthesis. The inferior and lateral cortices are cut to the length of the prosthetic head and the superior ledge is retained. The articular surface of the proximal phalanx is removed. A trial reduction of the two components is done to assess the need for soft tissue release. However, if possible, the collateral ligaments should be retained. Bone cement is inserted into each canal and the components are inserted. The prosthesis is articulated by a snap fit. Wound closure is standard. Schultz was present to provide instruction during the implanting of the first 20 prostheses. The original prosthetic design was used in all fingers. A metallic hinge prosthesis of the Flatt design was inserted in 12 ipsilateral proximal interphalangeal (PIP) joints during the same operation. Results
The results of 36 Schultz MP joint replacements, with an average follow-up of 10.9 years were reviewed. Since a metallic hinge prosthesis had been inserted in one third of the PIP joints, an evaluation of the PIP joint was not included. Before operation, the average active range of motion (AROM) of all MP joints was 31 degrees, with an average arc of motion from 64 degrees extension to 95 degrees flexion. At the 3-year
follow-up, the AROM was 32 degrees, with an arc from 40 degrees to 72 degrees. At the 5-year follow-up, the AROM was 23 degrees, with an arc from 46 degrees to 69 degrees. At the final follow-up, the AROM was 10 degrees, with an arc from 58 degrees to 68 degrees. The progressive decrease in AROM of all MP joints is shown graphically in Fig. 1. There was a gradual recurrence toward a more flexed position. Ulnar deviation recurred in all digits. The average deviation was 32 degrees before operation, 15 degrees at 3 years, 20 degrees at 5 years, and 28 degrees at final follow-up. The degree of deviation was greater in fingers with broken implants. Extensor tendon dislocation recurred in the 27 fingers with recurrent ulnar deviation greater than 20 degrees. Palmar subluxation recurred only in the fingers with a fractured prosthesis (14 fingers). Average preoperative key pinch was 3.2 kg and grip strength was 8.8 kg. The 3-year and 5-year measurements showed a gradual decline, with final measurements of 1.9 kg and 2.9 kg, respectively. The patients judged their appearance and function to be improved in four cases, to be the same in one, and made worse in three. Radiographs showed a fracture through the neck of the metal proximal phalangeal component in 39% of the prostheses (Fig. 2). Fractures involved 5 index, 4 long, 3 ring, and 2 small fingers. Periarticular het-
Vol. 15A, No.4 July 1990
Fig. 2. Fracture of the neck-stem junction of the metallic proximal phalangeal component has occurred in all four fingers, with recurrence of ulnar drift; no component loosening.
erotopic bone formation occurred in all hands (Fig. 3). However, this was extensive in only 22%. A lucency of the bone-cement interface measuring Lto 3 mm was seen about the proximal (juxta-articular) 4 mm of the phalangeal component in 80%. This was always associated with a thickening or expansion of the cortex, but was less if there was component fracture. A similar, but less prominent change was seen about the distal (juxta-articular) portion of the metacarpal component in 36%. A complete 1 mm lucency of the bone-cement interface occurred about the stem of five phalangeal components. However, in all five fingers a PIP joint implant shared the same medullary canal, which made evaluation of changes difficult. A correlation of function and prosthetic fracture was done. Since all fractures had occurred within 5 years, the 3-year values were used for the analysis. The results show that a fracture did not occur if the MP joint had more than 25 degrees of AROM. Patients with greater than 6.4 kg grip strength or 5.5 kg pinch strength fractured at least one implant. However, one patient who had only 2.7 kg grip strength and 1.4 kg pinch strength fractured two implants.
Schultz MP arthroplasty
643
Fig. 3. Periarticular heterotopic bone formation is seen in all four fingers. Lucency of the bone-cement interface is present about the juxta-articular portion of the components. Index and long finger components have fractured; no component loosening.
Six of the 12 PIP joint implants that were inserted concurrently with a Schultz prosthesis were removed because of infection. To erradicate the infection in three of these six fingers, removal of a Schultz prosthesis from one finger and amputation of two fingers was required. In only one finger was a Schultz prosthesis removed because of infection unrelated to a PIP joint implant infection. This occurred in a woman who sustained a deep dorsal abrasion that exposed the joint. There was no evidence of hematogenous seeding as a cause of infection in this study group. Discussion A method for MP arthroplasty in the patient with rheumatoid arthritis that provides a satisfactory longterm result continues to elude hand surgeons. Although arthroplasty employing a silicone implant is widely used, the implant is not a true prosthesis and does not restore full motion or significantly improve strength. 6 In addition, problems with component fracture and recurrence of deformity are common. Physicians and engineers have attempted to design a prosthesis that duplicates the mechanics of the normal MP joint.
644
The Journal of HAND SURGERY
Adams, Blair, and Shurr
However, the design requirements are complex and demending." 7.8 These requirements have been analyzed in mathematical and laboratory models to quantitate the normal articular anatomy and joint forces.": 9. 10 Unfortunately, current mathematical models make many assumptions and have significant limitations.'! Schultz and colleagues" developed an experimental device that made direct measurements of the MP joint in three dimensions. The data was used to construct a computersimulated model of the MP joint. They claimed the collateral ligaments are taut in all positions of the flexion-extension arc and the MP joint moves with a changing axis of rotation. 2.12 Schultz applied these ideas in designing the prosthesis analyzed in this study. Gillespie'? performed a biomechanical evaluation of several MP joint implants including the Schultz prosthesis. The range of motion of the Schultz implant was neutral to 90 degrees of flexion, with an 8 degree arc of radial-ulnar deviation in extension, and no deviation in full flexion. The axis of rotation during flexionextension varied in an unpredictable manner and fingertip force measurements were inconsistent. The authors concluded that the variability in fingertip force was due to the unpredictable changing center of rotation. Therefore, the implant did not function according to the objective of the design in their study. In addition, cold flow deformation was seen in the articulated portion of the plastic metacarpal component. Rheumatoid arthritis causes an ulnar and palmar displacement of the force nucleus described by Zancolli. 14 Thus both static and dynamic forces are altered. To increase stability, the Schultz prosthesis is designed to retain the collateral ligaments. Unfortunately, this is possible only when resection of the proximal phalanx is minimal. The ball-in-socket design is intended to dampen the forces acting across the joint, thus decreasing the stress transmitted to bone. However, plastic deformation of the slot in the metacarpal component and fracture of the metallic neck of the phalangeal component contributed to recurrence of deformity. It appears the forces generated by routine use of the hand were greater than the prosthetic tolerances. An interesting finding in this study was the lack of component loosening. Although limited juxta-articular lucency of the bone-cement interface was seen in the majority of fingers, no frank loosening occurred. Therefore, the design of the Schultz prosthesis appears to be satisfactory for fixation in the medullary canals. However, long-term stable fixation appears to increase stresses in the articulated portion of the implant leading to frequent materials failure. Periarticular heterotopic bone formation is a common finding with all methods
of MP arthroplasty, but was more prominent in this study. The cause of the heterotopic bone is not clear. The bone formation often extends from a cut edge and follows the course of the retained collateral ligaments. This study is the longest reported follow-up of a cemented articulated MP joint prosthesis. The results indicate that long-term intramedullary cement fixation of relatively long-stemmed components can be satisfactory. However, the articulated portion of this implant does not consistently withstand the stresses transmitted across the joint and does not provide long-term stability. Clinical results measured in this study are similar to the results reported for silicone implants." 15 Although silicone implants continue to be widely used, their design does not provide an ideal biomechanical reconstruction of the MP joint. Further research and development is needed to design a better prosthesis that is both biologically and mechanically suited to the rheumatoid MP joint.
1.
2.
3.
4.
5.
6.
7.
8. 9.
10.
REFERENCES Flatt AB. Care of the arthritic hand. 4th ed. St Louis: The CV Mosby Co., 1983. SchultzRJ. Total metacarpophalangeal joint arthroplasty with limited metacarpal head resection. In: Inghs AE, ed. Symposium on total joint replacement of the upper extremity. American Academy Orthopedic Surgeons. St Louis: The CV Mosby Co., 1982:199-216. Steffee A. History, design and development of Steffee metacarpophalangeal prosthesis. In: Inghs AB, ed. Symposium on total joint replacementof the upper extremity. AmericanAcademy Orthopedic Surgeons. St Louis: The CV Mosby Co., 1982:179-86. Steffee AD, Beckenbaugh RD, Linscheid RL, Dobyns JH. The development, technique, and early clinical results of total joint replacementfor the metacarpophalangeal joint of the fingers. Orthopaedics 1981;4:175-80. Linscheid RL, Beckenbaugh RD, Dobyns JH, Cooney WP.Metacarpophalangeal arthroplasty withSteffee prostheses. In: Inghs AE, ed, Symposium on total joint replacement of the upper extremity. American Academy Orthopedic Surgeons. St Louis: The CV Mosby Co., 1982:187-98. Blair WF, Shurr DO, BuckwalterJA. Metacarpophalangeal joint implant arthroplasty with a silastic spacer. J Bone Joint Surg 1984;66A:365-70. Flatt AB, Fischer OW. Biomechanicalfactors in the replacement of rheumatoid finger joints. Ann Rheum Dis 1969;28(suppl):36-44. Neale MJ. Theoretical design of various types of finger joint. Ann Rheum Dis 1969;28(suppl):25-30. Smith EM, Juvinall RC, Bender LF, Pearson JR. Role of finger flexors in rheumatoid deformities of the metacarpophalangeal joints. Arthritis Rheum 1964;7:467-80. Flatt AB. The pathomechanics of ulnar drift: a biome-
Vol. 15A, No.4 July 1990
chanical and clinical study. Social and Rehabilitation Services, grant no. RD 2226M, 1971. 11. Linscheid RL, Chao EY. Biomechanical assessment of finger function in prosthetic joint design. Orthop Clin North Am 1973;4:317-30. 12. Schultz RJ, Storace A. A new viewpoint on metacarpophalangeal joint motion and the role of the collateral ligaments. J HAND SURG 1978;3:291. 13. Gillespie TE, Flatt AB, Youm Y, Sprague BL. Blome-
Schultz MP arthroplasty
chanical evaluation of metacarpophalangeal joint prosthesis designs. J HAND SURG 1979;4:508-21. 14. Zancolli E. Structural and dynamic bases of hand surgery. Philadelphia: JB Lippincott, 1979. 15. Goldner JL, Gould JS, Urbaniak JR, McCollum DE. Metacarpophalangeal joint arthroplasty with siliconeDacron prostheses (Niebauer type): six and a half years experience. J HAND SURG 1977;2:200-11.
A splint for controlled active motion after flexor tendon repair Design, mechanical testing, and preliminary clinical results A splint for controlled active motion after flexor tendon repair is described. It incorporates a single core-coated elastic band passing around a palmar pulley and attached proximally to a spring wire. Its mechanical properties were tested against six other systems. The tension in various systems all rose near full extension. However, the palmar pulley, the spring wire, and the elastic band each could lower the tension significantly. When the bending moments at the interphalangeal joints were measured, all systems produced a peak during the latter part of extension. With the palmar pulley, spring wire, and elastic band, the rise was minimal and in fact, the bending moments diminished near full extension. Initial results in 28 flexor tendon repairs using this splint showed less flexion contracture when compared with 78 flexor tendon repairs using a standard rubber baud anchored at the wrist. (J HAND SURG 1990ilSA:645-Sl,)
S. P. Chow, MS, FRCSE, FACS, M. M. Stephens, MS, FRCSI, W. K. Ngai, FRCSE, Y. C. So, FRCS, FRCSE, FRACS, W. K. Pun, MCh(Orth), FRCSG, FReSE, FRACS, M. Chu, OTR, and C. Crosby, MCSP, Hong Kong
Nowadays there is great emphasis on a meticulous postoperative program following flexor tendon repair. 1-7 The concept of controlled early mobilization that was popularized by Kleinert et al. 8 aimed From the Departments of Orthopaedic Surgery,Occupation Therapy,
and Physiotherapy, University of Hong Kong, Queen Mary Hospital, Hong Kong. Received tor publication March 2, 1989; accepted in revised form Aug. 3, 1989. No benefits in any form have been received or will bereceived from a commercial party related directly or indirectly to the subject of this article. Reprint requests: S. P. Chow, MS, FRCSE, FACS, Department of Orthopaedic Surgery, University of HongKong, Queen MaryHospital, Hong Kong, 5-8192258. 3/1/16645
at protected gliding of the repaired tendon using a special splint, thus minimizing the formation of thick tendon adhesions. However, the rubber band traction system that Kleinert et al. 8 originally used produced a sharp rise in tension at the last 20 to 30 degrees of extension, consequently leading to flexion contracture of the proximal interphalangeal (PIP) joint. Frequently, splintage at 6 to 8 weeks is required to correct this contracture. 9 To overcome this problem, various methods had been devised to produce a more "constant" tension, such as the use of a much longer rubber band anchored at the proximal forearm or the incorporation of a roller wheel system. IO The direction of pull of the original Kleinert rubber band traction system also did not allow full flexion at the distal interphalangeal (DIP) joint, and therefore, did not allow much movement at this joint. As THE JOURNAL OF HAND SURGERY
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