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Synovial Osteochondromatosis of the Hip Treated Through a Surgical Dislocation
The Journal of Arthroplasty Vol. 24 No. 7 2009
Case Report
Synovial Osteochondromatosis of the Hip Treated Through a Surgical Dislocation Yoshihide Nakamura, MD,* Naoki Echigoya, MD,*y and Satoshi Toh, MD*
Abstract: We report a case of osteochondromatosis in the hip joint treated through a surgical dislocation and describe the use and safety of the procedure confirmed by postoperative magnetic resonance imaging. A 44-year-old man had right hip pain with moderate limitation of the range of motion. Plain radiographs and computed tomography showed calcified loose bodies in the hip with mild joint degeneration. Magnetic resonance imaging showed remarkable expansion of the capsule containing joint fluid and loose bodies below the femoral head. Complete removal of loose bodies and synovectomy were performed through a surgical dislocation. Three months after the operation, the patient had fully recovered and returned to his job. Magnetic resonance imaging performed 5 months after surgery revealed full removal of the loose bodies and no recurrence of the disease including synovial proliferation. It also showed no evidence of avascular necrosis, meaning that the procedure had been performed safely. Keywords: osteochondromatosis, surgical dislocation of the hip, MRI. © 2009 Elsevier Inc. All rights reserved.
Primary synovial osteochondromatosis is a rarely seen disorder of the synovium in any joints. This condition is most often seen in the knee, and the hip joint is even more rarely affected. Treatment of this condition is essentially to remove the loose bodies [1-3]. Surgical dislocation of the hip is undertaken infrequently because there is little information on how to avoid osteonecrosis of the femoral head, despite the emphasized danger to the vascularity of the femoral head. Recently, Ganz et al [4] reported surgical dislocation of the hip as a safe and useful procedure based on detailed anatomical study. We report a case of osteochondromatosis in the hip joint treated through a surgical dislocation and From the *Department of Orthopaedic Surgery, Hirosaki University Graduate School of Medicine, Aomori, Japan; and yDepartment of Orthopaedic Surgery, Kuroishi Hospital, Japan. Submitted June 28, 2008; accepted September 5, 2008. No benefits or funds were received in support of this study. Reprint requests: Yoshihide Nakamura, MD, Department of Orthopaedic Surgery, Hirosaki University Graduate School of Medicine, Zaifu-cho, Hirosaki City, Aomori 036-8562, Japan. © 2009 Elsevier Inc. All rights reserved. 0883-5403/08/2407-0026$36.00/0 doi:10.1016/j.arth.2008.09.004
describe the use and safety of the procedure confirmed by postoperative magnetic resonance imaging (MRI).
Case Report A 44-year-old man had right hip pain spontaneously for a year before his first visit to our hospital. The symptoms worsened despite conservative treatments including administration of analgesics and intra-articular injection of steroid and local anesthetic. One year after the first visit to our institution, he was hospitalized for surgical treatment. His affected right hip showed moderate limitation of the range of motion. Flexion of the hip was limited to 100°, external rotation to 20°, and internal rotation to 20°. He also complained of hip pain in flexion and rotation of the hip. He felt severe tenderness in the Scarpa's triangle in the hip. Plain radiographs showed calcified loose bodies in the hip with mild joint degeneration including irregularity of the articular surface of the femoral head (Fig. 1). Computed tomography also revealed
1143.e15
1143.e16 The Journal of Arthroplasty Vol. 24 No. 7 October 2009
Fig. 1. Preoperative radiographs showed multiple calcified loose bodies filling the hip joint. Superolateral portion of the femoral head was irregular, indicating degenerative changes of the joint.
multiple calcified free bodies extending around the femoral neck from anterior to posterior and in the acetabular fossa (Fig. 2). Magnetic resonance imaging
showed remarkable expansion of the capsule containing joint fluid and free bodies below the femoral head. Free bodies showing low signal T1-weighted image
Fig. 2. Computed tomography revealed multiple loose bodies in the acetabular fossa. They were extensively present around the femoral neck from anterior to posterior.
Synovial Osteochondromatosis of the Hip Treated Through a Surgical Dislocation Nakamura et al
1143.e17
Fig. 3. A, T1-weighted magnetic resonance image (MRI) showed fluid collection in the inferomedial portion of the joint and high signal lesions indicating fatty tissue in the acetabular fossa. B, T2-weighted MRI indicated multiple loose bodies with low signal intensity around the femoral neck and inferomedial portion of the capsular sac. High signal lesions in the acetabular fossa were also seen in this image.
(Fig. 3A) and low to intermediate in T2 were also seen around the basal femoral neck (Fig. 3B). Proliferation of the fibrofatty synovial tissue was seen in the acetabular fossa. Magnetic resonance imaging did not show extra-articular expansion of the disease. Removal of loose bodies and synovectomy were performed through a surgical dislocation. The greater trochanter was osteotomized, and the joint was anteriorly dislocated. Ninety-two free bodies were entirely removed. The size of the largest loose body was 20 × 13-mm diameter. Proliferated synovium in the acetabular fossa was excised. The osteotomized greater trochanter was anatomically repositioned and fixed by an absorbable screw without repairing the capsule (Fig. 4).
Histologic study of the loose bodies showed characteristic findings of synovial osteochondromatosis (Fig. 5). Clustered chondrocytes were observed in hyaline cartilage tissue surrounded by synovial membrane. Calcification was identified beneath the synovium. According to the Milgram [2] criteria for staging synovial osteochondromatosis, this case was phase 3 (multiple free bodies due to synovial osteochondromatosis with normal or slightly inflamed synovium). Three months after the operation, the patient had fully recovered and returned to his job. He had no hip pain, and the range of motion of the affected hip had improved but was slightly limited compared with the other hip. Postoperative radiograph
Fig. 4. Loose bodies spilled out through the capsulotomy. Focal erosions of the articular cartilage of the femoral head were seen at surgery. Ninety-two free bodies were entirely removed from the joint. The size of the largest one was 20 × 13-mm diameter.
1143.e18 The Journal of Arthroplasty Vol. 24 No. 7 October 2009 necrosis of the femoral head. The greater trochanter was securely fixed in the anatomical position (Fig. 6A). Magnetic resonance imaging performed 5 months after surgery revealed full removal of the loose bodies and no recurrence of the disease including synovial proliferation. Magnetic resonance imaging also showed no findings of avascular necrosis of the femoral head, meaning there was no iatrogenic impairment of blood circulation of the femoral head in both T1-weighted and T2-weighted images (Fig. 6B and C).
Discussion Fig. 5. Clustered chondrocytes (arrow head) were seen in hyaline cartilage tissue surrounded by synovial membrane (asterisk). Focal calcification (arrow) was identified beneath the synovium (hematoxylin and eosin, original magnification ×40).
showed complete removal of the loose bodies. Degenerative change of the joint was not progressed, and there were no findings of avascular
Synovial osteochondromatosis is a condition that rarely affects the hip joint [2,5]. If the calcification or ossification of the loose bodies as seen in our case is apparent, it is relatively easy to diagnose. Magnetic resonance imaging is useful and essential for diagnosis of the condition when calcification does not exist [6]. Lim et al [5] reported the usefulness of MRI in early diagnosis of synovial chondromatosis
Fig. 6. The loose bodies were entirely removed in postoperative radiograph. Degenerative change of the joint had not progressed, and there were no findings of avascular necrosis of the femoral head. The osteotomized greater trochanter was fixed in the anatomical position (A). Magnetic resonance imaging at 5 months after surgery revealed complete removal of the loose bodies and no recurrence of the disease including synovial proliferation. Magnetic resonance imaging also showed no findings of avascular necrosis of the femoral head, meaning iatrogenic impairment of blood circulation of the femoral head in both T1-weighted and T2-weighted images (B and C). Fluid collection at the inferior portion of the capsule was seen in T2-weighted image.
Synovial Osteochondromatosis of the Hip Treated Through a Surgical Dislocation Nakamura et al
of the hip. Magnetic resonance imaging is also worthwhile to perform to search for extra-articular extension of the disease [6]. In our case, we could know preoperatively that the lesions in our case were intra-articular. Treatment of osteochondromatosis includes excision of loose bodies and synovectomy. Total excision of loose bodies is essential for relief of symptoms including pain and limitation of motion and for prevention of further progression of articular degeneration [1,5,7,8]. Ogilvie-Harris and Saleh [3] reported the importance of synovectomy combined with removal of loose bodies to avoid clinical recurrence in osteochondromatosis of the knee joint. Some authors recommended synovectomy with removal of the loose bodies in the hip joint for the same reason [5]. Recently, many surgeons have reported arthroscopic procedures for treatment of this condition [7,8], but as Lim et al [5] reported, we consider arthroscopic surgery of the hip to be very technically demanding. In our case, the free bodies extensively expanded throughout the joint anteriorly to posteriorly. Some of the loose bodies showed large diameter, which makes total arthroscopic removal difficult. It is also easy to damage the articular cartilage during arthroscopic surgery, and the procedure can require a much longer operating time. Some authors have reported treatment of synovial osteochondromatosis of the hip joint through a dislocation of the joint [4,5]. The most worrisome thing about surgical dislocation of the hip is occurrence of postoperative osteonecrosis of the femoral head. Gautier et al [9] described the detailed anatomy of the vascularity of the femoral head, and they concluded that surgical dislocation of the joint is safe as long as disruption of the obturator externus muscle is avoided during surgery. Ganz et al [4] reported a safe and useful technique for the surgical dislocation of the hip joint. These reports ruled out postoperative osteonecrosis of the femoral head by plain radiographs only. We confirmed absence of necrosis by MRI. Poggi et al [10] reported MRI could be used with confidence for the early detection of osteonecrosis of the femoral head after traumatic hip dislocation or fracture-dislocation. According to this report, posttraumatic necrosis of the femoral head never occurs in joints that show normal signal in MRI 4 to 6 weeks after traumatic dislocation. Sugano et al [11] reported a prospective study of 17 patients with transcervical fracture of the femoral neck treated by internal fixation with 4.4 years of follow-up. The hip that showed no changes on MRI at 1 month after injury had no abnormal findings on
1143.e19
physical examination, radiography, or MRI at final follow-up in the study. In our case, MRI was performed 5 months after surgery and showed no evidence of avascular necrosis. We believe this is sufficient to confirm the procedure was safely performed. Kim et al [6] reported MRI is useful for diagnosis of osteochondromatosis especially in the early stage by confirming synovial proliferation and the presence of intra-articular bodies of focal low signal intensity at all pulse sequences, with areas of isointensity on T1-weighted image and hyperintensity on T2-weighted image. We believe MRI is useful for detecting recurrence of the lesion in the early phase after surgical treatment if it is economically feasible for patients to have routine postoperative MRI at regular follow-up intervals (eg, once a year).
References 1. Krebs VE. The role of hip arthroscopy in the treatment of synovial disorders and loose bodies. Clin Orthop Relat Res 2003;406:48. 2. Milgram JW. Synovial osteochondromatosis: a histopathological study of thirty cases. J Bone Joint Surg Am 1977;59:792. 3. Ogilvie-Harris DJ, Saleh K. Generalized synovial chondromatosis of the knee: a comparison of removal of the loose bodies alone with arthroscopic synovectomy. Arthroscopy 1994;10:166. 4. Ganz R, Gill TJ, Gautier E, et al. Surgical dislocation of the adult hip: a technique with full access to the femoral head and acetabulum without the risk of avascular necrosis. J Bone Joint Surg Br 2001;83: 1119. 5. Lim SJ, Chung HW, Choi YL, et al. Operative treatment of primary synovial osteochondromatosis of the hip. J Bone Joint Surg Am 2006;88:2456. 6. Kim SH, Hong SJ, Park JS, et al. Idiopathic synovial osteochondromatosis of the hip: radiographic and MR appearances in 15 patients. Korean J Radiol 2002;3: 254. 7. Okada Y, Awaya G, Ikeda T, et al. Arthroscopic surgery for synovial chondromatosis of the hip. J Bone Joint Surg Br 1989;71:198. 8. Witwity T, Uhlmann RD, Fischer J. Arthroscopic management of chondromatosis of the hip joint. Arthroscopy 1988;4:55. 9. Gautier E, Ganz K, Krügel N, et al. Anatomy of the medial femoral circumflex artery and its surgical implications. J Bone Joint Surg Br 2000;82-B:679. 10. Poggi JJ, Callaghan JJ, Spritzer CE, et al. Changes on magnetic resonance images after traumatic hip dislocation. Clin Orthop Relat Res 1995;319:249. 11. Sugano N, Masuhara K, Nakamura N, et al. MRI of early osteonecrosis of the femoral head after transcervical fracture. J Bone Joint Surg Br 1996;78:253.
Case Report
Synovial Osteochondromatosis of the Hip Treated Through a Surgical Dislocation Yoshihide Nakamura, MD,* Naoki Echigoya, MD,*y and Satoshi Toh, MD*
Abstract: We report a case of osteochondromatosis in the hip joint treated through a surgical dislocation and describe the use and safety of the procedure confirmed by postoperative magnetic resonance imaging. A 44-year-old man had right hip pain with moderate limitation of the range of motion. Plain radiographs and computed tomography showed calcified loose bodies in the hip with mild joint degeneration. Magnetic resonance imaging showed remarkable expansion of the capsule containing joint fluid and loose bodies below the femoral head. Complete removal of loose bodies and synovectomy were performed through a surgical dislocation. Three months after the operation, the patient had fully recovered and returned to his job. Magnetic resonance imaging performed 5 months after surgery revealed full removal of the loose bodies and no recurrence of the disease including synovial proliferation. It also showed no evidence of avascular necrosis, meaning that the procedure had been performed safely. Keywords: osteochondromatosis, surgical dislocation of the hip, MRI. © 2009 Elsevier Inc. All rights reserved.
Primary synovial osteochondromatosis is a rarely seen disorder of the synovium in any joints. This condition is most often seen in the knee, and the hip joint is even more rarely affected. Treatment of this condition is essentially to remove the loose bodies [1-3]. Surgical dislocation of the hip is undertaken infrequently because there is little information on how to avoid osteonecrosis of the femoral head, despite the emphasized danger to the vascularity of the femoral head. Recently, Ganz et al [4] reported surgical dislocation of the hip as a safe and useful procedure based on detailed anatomical study. We report a case of osteochondromatosis in the hip joint treated through a surgical dislocation and From the *Department of Orthopaedic Surgery, Hirosaki University Graduate School of Medicine, Aomori, Japan; and yDepartment of Orthopaedic Surgery, Kuroishi Hospital, Japan. Submitted June 28, 2008; accepted September 5, 2008. No benefits or funds were received in support of this study. Reprint requests: Yoshihide Nakamura, MD, Department of Orthopaedic Surgery, Hirosaki University Graduate School of Medicine, Zaifu-cho, Hirosaki City, Aomori 036-8562, Japan. © 2009 Elsevier Inc. All rights reserved. 0883-5403/08/2407-0026$36.00/0 doi:10.1016/j.arth.2008.09.004
describe the use and safety of the procedure confirmed by postoperative magnetic resonance imaging (MRI).
Case Report A 44-year-old man had right hip pain spontaneously for a year before his first visit to our hospital. The symptoms worsened despite conservative treatments including administration of analgesics and intra-articular injection of steroid and local anesthetic. One year after the first visit to our institution, he was hospitalized for surgical treatment. His affected right hip showed moderate limitation of the range of motion. Flexion of the hip was limited to 100°, external rotation to 20°, and internal rotation to 20°. He also complained of hip pain in flexion and rotation of the hip. He felt severe tenderness in the Scarpa's triangle in the hip. Plain radiographs showed calcified loose bodies in the hip with mild joint degeneration including irregularity of the articular surface of the femoral head (Fig. 1). Computed tomography also revealed
1143.e15
1143.e16 The Journal of Arthroplasty Vol. 24 No. 7 October 2009
Fig. 1. Preoperative radiographs showed multiple calcified loose bodies filling the hip joint. Superolateral portion of the femoral head was irregular, indicating degenerative changes of the joint.
multiple calcified free bodies extending around the femoral neck from anterior to posterior and in the acetabular fossa (Fig. 2). Magnetic resonance imaging
showed remarkable expansion of the capsule containing joint fluid and free bodies below the femoral head. Free bodies showing low signal T1-weighted image
Fig. 2. Computed tomography revealed multiple loose bodies in the acetabular fossa. They were extensively present around the femoral neck from anterior to posterior.
Synovial Osteochondromatosis of the Hip Treated Through a Surgical Dislocation Nakamura et al
1143.e17
Fig. 3. A, T1-weighted magnetic resonance image (MRI) showed fluid collection in the inferomedial portion of the joint and high signal lesions indicating fatty tissue in the acetabular fossa. B, T2-weighted MRI indicated multiple loose bodies with low signal intensity around the femoral neck and inferomedial portion of the capsular sac. High signal lesions in the acetabular fossa were also seen in this image.
(Fig. 3A) and low to intermediate in T2 were also seen around the basal femoral neck (Fig. 3B). Proliferation of the fibrofatty synovial tissue was seen in the acetabular fossa. Magnetic resonance imaging did not show extra-articular expansion of the disease. Removal of loose bodies and synovectomy were performed through a surgical dislocation. The greater trochanter was osteotomized, and the joint was anteriorly dislocated. Ninety-two free bodies were entirely removed. The size of the largest loose body was 20 × 13-mm diameter. Proliferated synovium in the acetabular fossa was excised. The osteotomized greater trochanter was anatomically repositioned and fixed by an absorbable screw without repairing the capsule (Fig. 4).
Histologic study of the loose bodies showed characteristic findings of synovial osteochondromatosis (Fig. 5). Clustered chondrocytes were observed in hyaline cartilage tissue surrounded by synovial membrane. Calcification was identified beneath the synovium. According to the Milgram [2] criteria for staging synovial osteochondromatosis, this case was phase 3 (multiple free bodies due to synovial osteochondromatosis with normal or slightly inflamed synovium). Three months after the operation, the patient had fully recovered and returned to his job. He had no hip pain, and the range of motion of the affected hip had improved but was slightly limited compared with the other hip. Postoperative radiograph
Fig. 4. Loose bodies spilled out through the capsulotomy. Focal erosions of the articular cartilage of the femoral head were seen at surgery. Ninety-two free bodies were entirely removed from the joint. The size of the largest one was 20 × 13-mm diameter.
1143.e18 The Journal of Arthroplasty Vol. 24 No. 7 October 2009 necrosis of the femoral head. The greater trochanter was securely fixed in the anatomical position (Fig. 6A). Magnetic resonance imaging performed 5 months after surgery revealed full removal of the loose bodies and no recurrence of the disease including synovial proliferation. Magnetic resonance imaging also showed no findings of avascular necrosis of the femoral head, meaning there was no iatrogenic impairment of blood circulation of the femoral head in both T1-weighted and T2-weighted images (Fig. 6B and C).
Discussion Fig. 5. Clustered chondrocytes (arrow head) were seen in hyaline cartilage tissue surrounded by synovial membrane (asterisk). Focal calcification (arrow) was identified beneath the synovium (hematoxylin and eosin, original magnification ×40).
showed complete removal of the loose bodies. Degenerative change of the joint was not progressed, and there were no findings of avascular
Synovial osteochondromatosis is a condition that rarely affects the hip joint [2,5]. If the calcification or ossification of the loose bodies as seen in our case is apparent, it is relatively easy to diagnose. Magnetic resonance imaging is useful and essential for diagnosis of the condition when calcification does not exist [6]. Lim et al [5] reported the usefulness of MRI in early diagnosis of synovial chondromatosis
Fig. 6. The loose bodies were entirely removed in postoperative radiograph. Degenerative change of the joint had not progressed, and there were no findings of avascular necrosis of the femoral head. The osteotomized greater trochanter was fixed in the anatomical position (A). Magnetic resonance imaging at 5 months after surgery revealed complete removal of the loose bodies and no recurrence of the disease including synovial proliferation. Magnetic resonance imaging also showed no findings of avascular necrosis of the femoral head, meaning iatrogenic impairment of blood circulation of the femoral head in both T1-weighted and T2-weighted images (B and C). Fluid collection at the inferior portion of the capsule was seen in T2-weighted image.
Synovial Osteochondromatosis of the Hip Treated Through a Surgical Dislocation Nakamura et al
of the hip. Magnetic resonance imaging is also worthwhile to perform to search for extra-articular extension of the disease [6]. In our case, we could know preoperatively that the lesions in our case were intra-articular. Treatment of osteochondromatosis includes excision of loose bodies and synovectomy. Total excision of loose bodies is essential for relief of symptoms including pain and limitation of motion and for prevention of further progression of articular degeneration [1,5,7,8]. Ogilvie-Harris and Saleh [3] reported the importance of synovectomy combined with removal of loose bodies to avoid clinical recurrence in osteochondromatosis of the knee joint. Some authors recommended synovectomy with removal of the loose bodies in the hip joint for the same reason [5]. Recently, many surgeons have reported arthroscopic procedures for treatment of this condition [7,8], but as Lim et al [5] reported, we consider arthroscopic surgery of the hip to be very technically demanding. In our case, the free bodies extensively expanded throughout the joint anteriorly to posteriorly. Some of the loose bodies showed large diameter, which makes total arthroscopic removal difficult. It is also easy to damage the articular cartilage during arthroscopic surgery, and the procedure can require a much longer operating time. Some authors have reported treatment of synovial osteochondromatosis of the hip joint through a dislocation of the joint [4,5]. The most worrisome thing about surgical dislocation of the hip is occurrence of postoperative osteonecrosis of the femoral head. Gautier et al [9] described the detailed anatomy of the vascularity of the femoral head, and they concluded that surgical dislocation of the joint is safe as long as disruption of the obturator externus muscle is avoided during surgery. Ganz et al [4] reported a safe and useful technique for the surgical dislocation of the hip joint. These reports ruled out postoperative osteonecrosis of the femoral head by plain radiographs only. We confirmed absence of necrosis by MRI. Poggi et al [10] reported MRI could be used with confidence for the early detection of osteonecrosis of the femoral head after traumatic hip dislocation or fracture-dislocation. According to this report, posttraumatic necrosis of the femoral head never occurs in joints that show normal signal in MRI 4 to 6 weeks after traumatic dislocation. Sugano et al [11] reported a prospective study of 17 patients with transcervical fracture of the femoral neck treated by internal fixation with 4.4 years of follow-up. The hip that showed no changes on MRI at 1 month after injury had no abnormal findings on
1143.e19
physical examination, radiography, or MRI at final follow-up in the study. In our case, MRI was performed 5 months after surgery and showed no evidence of avascular necrosis. We believe this is sufficient to confirm the procedure was safely performed. Kim et al [6] reported MRI is useful for diagnosis of osteochondromatosis especially in the early stage by confirming synovial proliferation and the presence of intra-articular bodies of focal low signal intensity at all pulse sequences, with areas of isointensity on T1-weighted image and hyperintensity on T2-weighted image. We believe MRI is useful for detecting recurrence of the lesion in the early phase after surgical treatment if it is economically feasible for patients to have routine postoperative MRI at regular follow-up intervals (eg, once a year).
References 1. Krebs VE. The role of hip arthroscopy in the treatment of synovial disorders and loose bodies. Clin Orthop Relat Res 2003;406:48. 2. Milgram JW. Synovial osteochondromatosis: a histopathological study of thirty cases. J Bone Joint Surg Am 1977;59:792. 3. Ogilvie-Harris DJ, Saleh K. Generalized synovial chondromatosis of the knee: a comparison of removal of the loose bodies alone with arthroscopic synovectomy. Arthroscopy 1994;10:166. 4. Ganz R, Gill TJ, Gautier E, et al. Surgical dislocation of the adult hip: a technique with full access to the femoral head and acetabulum without the risk of avascular necrosis. J Bone Joint Surg Br 2001;83: 1119. 5. Lim SJ, Chung HW, Choi YL, et al. Operative treatment of primary synovial osteochondromatosis of the hip. J Bone Joint Surg Am 2006;88:2456. 6. Kim SH, Hong SJ, Park JS, et al. Idiopathic synovial osteochondromatosis of the hip: radiographic and MR appearances in 15 patients. Korean J Radiol 2002;3: 254. 7. Okada Y, Awaya G, Ikeda T, et al. Arthroscopic surgery for synovial chondromatosis of the hip. J Bone Joint Surg Br 1989;71:198. 8. Witwity T, Uhlmann RD, Fischer J. Arthroscopic management of chondromatosis of the hip joint. Arthroscopy 1988;4:55. 9. Gautier E, Ganz K, Krügel N, et al. Anatomy of the medial femoral circumflex artery and its surgical implications. J Bone Joint Surg Br 2000;82-B:679. 10. Poggi JJ, Callaghan JJ, Spritzer CE, et al. Changes on magnetic resonance images after traumatic hip dislocation. Clin Orthop Relat Res 1995;319:249. 11. Sugano N, Masuhara K, Nakamura N, et al. MRI of early osteonecrosis of the femoral head after transcervical fracture. J Bone Joint Surg Br 1996;78:253.