Preservation technique of the piriformis tendon is superior to reattachment technique in terms of contiguity and muscle atrophy: using magnetic resonance imaging.

PURPOSE: The preservation technique of the piriformis tendon during the posterolateral approach in total hip arthroplasty (THA) is reportedly superior to the reattachment technique in terms of dislocation. However, the long-term effects of preservation of the piriformis tendon during THA remain unknown. In this study, we evaluated the contiguity of the piriformis/conjoined tendon and atrophy of the piriformis/internal obturator muscle during a long-term postoperative follow-up using magnetic resonance imaging (MRI). METHODS: We retrospectively evaluated 48 patients with available MRI. The 48 patients were classified into a P group ( n = 29), in which the piriformis tendon was preserved, and an R group ( n = 19), in which the piriformis was reattached after sectioning. The mean follow-up duration was 45.9 months. The contiguity of the piriformis/conjoined tendon and atrophy of the piriformis/internal obturator muscle were evaluated in all patients. RESULTS: The piriformis tendon remained attached to the greater trochanter in all P-group patients and 68.4% of R-group patients. The mean piriformis muscle atrophy ratios were 15.9% ± 21.1% in the P group and 41.6% ± 19.1% in the R group ( p < 0.001). The conjoined tendon repair remained intact in 72.4% of P-group patients and 36.8% of R-group patients ( p < 0.05). The mean internal obturator muscle atrophy ratio was 31.4% ± 26.2% in the P group and 50.4% ± 19.1% in the R group ( p < 0.05). No postoperative pulmonary embolism, wound infection, deep infection, or hip dislocation occurred. CONCLUSIONS: In our study, we suggest that the preservation technique of the piriformis tendon is superior to the reattachment technique in terms of contiguity and muscle atrophy.

Chondrolipoma of the Ankle in a Child: A Case Report.

Chondrolipoma is an extremely rare variant of lipoma with cartilaginous metaplasia. The presence of nonlipomatous components can lead to a variety of entities in the differential diagnosis from the radiologic findings. We describe an unusual case of a chondrolipoma occurring in the right ankle of a 9-year-old female. Physical examination showed a 3.5-cm, elastic-hard, poorly mobile, nontender mass adherent to the Achilles tendon. Plain radiographs revealed a faintly calcified soft tissue mass without bone involvement. Magnetic resonance imaging showed a well-defined mass with 2 components with heterogeneous signal intensity, suggesting the coexistence of a fatty area and another nonlipomatous component. Marginal excision of the tumor was performed. Histologically, the tumor was composed of mature adipose tissue studded with islands of mature hyaline cartilage. Based on these findings, the tumor was diagnosed as a chondrolipoma. The patient had no evidence of local recurrence within 9 months of follow-up. To the best of our knowledge, this is the first case of chondrolipoma originating from the ankle in a child.

Biomechanical comparison of the fixation after curved periacetabular osteotomy using titanium and bioabsorbable screws.

PURPOSE: We performed curved periacetabular osteotomy, a modification of the Bernese periacetabular osteotomy, to treat hip dysplasia. The purpose of our study was to compare the biomechanical stability of acetabular fragments fixed in place with 3 titanium screws, or with 2 or 3 bioabsorbable screws composed of particulate resorbable uncalcined hydroxyapatite (HA) and poly-L-lactic acid (PLLA) termed HA/PLLA screws. METHODS: Curved periacetabular osteotomy was performed on 24 composite model hemipelves. Three groups of 8 specimens were affixed with 1) 3 titanium screws, 2) 2 HA/PLLA screws, or 3) 3 HA/PLLA screws. After fixation, the hemipelves were biomechanically attested with simulated push-off phase of the gait cycle using a servohydraulic material testing system. RESULTS: The average failure loads were not significantly different among the3 groups tested. However, the group repaired with 3 HA/PLLA screws showed significantly greater stiffness than the other groups. CONCLUSIONS: All 3 fixation methods provided sufficient stability to allow for early partial weight-bearing after surgery. The use of 3 HA/PLLA screws provided significantly greater stiffness for acetabular fragment fixation.

A periacetabular osteotomy for the treatment of severe dysplastic hips.

BACKGROUND: We believe a curved periacetabular osteotomy is indicated for treatment of severe dysplastic hips with center-edge angles less than 0°, classified as Severin Group IV-b. However, the lower limit of the center-edge angle in hips classified as Severin Group IV-b is not clearly defined to determine which patients should receive periacetabular osteotomy alone. QUESTIONS/PURPOSES: We retrospectively compared the results of curved periacetabular osteotomies performed for the treatment of severe (Severin Group IV-b: center-edge angle < 0°) and moderate (Severin Groups III and IV-a: center-edge angle ≥ 0°) dysplastic hips. We investigated the lower limit of the center-edge angle, which was corrected by a curved periacetabular osteotomy alone in Severin Group IV-b hips. PATIENTS AND METHODS: We divided 191 hips in 163 patients into moderate (147 hips) and severe (44 hips) dysplastic hip groups. Minimum followup was 2 years (mean, 70.9 and 70.6 months, respectively). Clinical evaluations were performed using the Harris hip score. Radiographic measurements included the center-edge angle, acetabular head index, acetabular roof obliquity, and head lateralization index. Complications were compared between the two groups. RESULTS: All clinical and radiographic postoperative parameters showed satisfactory improvement over the preoperative parameters in both groups. The postoperative acetabular roof obliquity and head lateralization index were equivalent between the two groups. Eleven hips deteriorated to end-stage osteoarthritis. No complications were specifically associated with the severe dysplastic hips. CONCLUSIONS: Curved periacetabular osteotomy alone for treatment of severe dysplastic hips with preoperative center-edge angles as low as -20° and classified as Severin Group IV-b restored weightbearing area and medialization.

Is the obturator artery safe when performing ischial osteotomy during periacetabular osteotomy?

The purposes of this study were (1) to evaluate the actual distance between the obturator artery and the ischial osteotomy site when performing periacetabular osteotomy via an anterior approach and (2) to determine a safe method to avoid injuring the obturator artery during this procedure. Twenty-nine hemipelves from cadavers were used in this study. The mean distance between the obturator artery and the ischial osteotomy site was 35.6 ± 7.5 mm and always exceeded 20 mm. Therefore, the procedure can be performed safely when a chisel blade of 20 mm or shorter is used.

Intraoperative muscle damage in total hip arthroplasty.

Tenderness in the medial and posterior thigh is sometimes observed during the early postoperative period after total hip arthroplasty (THA). In this study, the possible correlations of preoperative hip range of motion, surgical approach, and limb lengthening with postoperative muscle strain injury in THA were investigated. Sixty primary THA patients given the posterolateral approach or direct-lateral approach were examined. For comparison of the muscle strain injury in the 2 groups, we used magnetic resonance imaging. There were significant differences in postoperative thigh pain between cases in the posterolateral group with reduction of internal rotation and those with no reduction, and between cases in the direct-lateral group with reduction of external rotation and those with no reduction.

Ischemia of the lateral femoral cutaneous nerve during periacetabular osteotomy using Smith-Petersen approach.

BACKGROUND: Lateral femoral cutaneous nerve (LFCN) injury is a common complication in the Smith-Petersen approach to the hip. This complication may be induced by neural ischemia or direct trauma during the procedure. The purpose of this study was to investigate the relationship between the neural ischemia of LFCN and postoperative sensory disturbance. MATERIALS AND METHODS: Nineteen patients who underwent periacetabular osteotomy through the Smith-Petersen approach were investigated. To evaluate neural ischemia, we measured the blood flow of LFCN using a laser Doppler flowmetry. The measurements were performed before and after osteotomy at the point 1 cm distal from the lower border of the inguinal ligament. LFCN was retracted to the medial side during the procedure. There was no direct trauma to LFCN in all cases. Postoperative sensory disturbance was evaluated at 2 weeks, 3 months, and 1 year follow-up after surgery. RESULTS: After osteotomy, the blood flow of LFCN was decreased to 2.4 from 3.3 ml min(-1) 100 g(-1) when compared with that before osteotomy (P < 0.01). Postoperatively, 14 of 19 patients had sensory disturbance at 2 weeks, 8 of 19 patients at 3 months, and 2 of 19 patients at 1 year follow-up. The blood flows of both patients who had persistent symptoms over 1 year after surgery had been decreased by more than 50% during operation. CONCLUSIONS: Decrease of blood flow of LFCN by more than 50% seems to cause persistent symptoms after surgery through the Smith-Petersen approach even if direct trauma to the nerve is avoided. Excessive traction by retractors is thought to be the main cause of blood flow reduction.

Prevalence of femoroacetabular impingement in Asian patients with osteoarthritis of the hip.

Although femoroacetabular impingement (FAI) has recently been considered to be one of the causes of osteoarthritis (OA) of the hip, the exact pathogeneses and incidence of FAI and primary OA are unknown. The purposes of this study were to investigate the causes of hip OA in Japan and to clarify the prevalence of FAI in patients with hip OA. We retrospectively investigated 817 consecutive patients (946 hips) who underwent primary surgery with the diagnosis of OA of the hip. Clinical recordings and preoperative radiographs were evaluated to determine the cause of OA. There were 17 hips who had primary OA, of which six hips were determined to be FAI positive. The remaining 11 cases without FAI had primary OA of unknown aetiology. Our study has revealed that most hip OA cases were caused by developmental dysplasia of the hip. We only found a few cases (0.6%) with FAI in Japan.

Tibiofemoral contact areas and pressures in six high flexion knees.

The tibiofemoral articulating interfaces of six high flexion knee designs were examined using a standard testing protocol developed by Harris et al. [J Biomech 32:951-958 (1999)] to investigate the polyethylene insert contact areas and pressures. A load of 3600 N was applied for 10 s at 0, 30, 60, 90, 110, 135 and 155 degrees of flexion. Contact areas and pressures at the femoral-polyethylene insert interface were measured with a I-scan 4000 system. Up to 110 degrees of flexion, the VANGUARD RP HI-FLEX showed the highest contact area and lowest pressure. At the deep flexion angles, contact area decreased and contact pressure increased significantly in all knees. The NexGen series showed a constant contact area throughout the various flexion angles. In general, all high flexion knees could result in almost point contact in an extremely high range of motion.

Postoperative acetabular retroversion causes posterior osteoarthritis of the hip.

We retrospectively reviewed 68 hips in 62 patients with acetabular dysplasia who underwent curved periacetabular osteotomy. Among the 68 hips, 33 had acetabular retroversion (retroversion group) and 35 had anteversion (control group) preoperatively. All hips were evaluated according to the Harris hip score. Radiographic evaluations of acetabular retroversion and posterior wall deficiency were based on the cross-over sign and posterior wall sign, respectively. The clinical scores of the two groups at the final follow-up were similar. In the retroversion group, 12 hips had anteverted acetabulum postoperatively. The posterior wall sign disappeared in these hips, but remained in 21 hips with retroverted acetabulum postoperatively. Among the 21 hips with retroverted acetabulum, posterior osteoarthritis of the hip developed postoperatively in five hips. When performing corrective osteotomy for a dysplastic hip with acetabular retroversion, it is important to correct the acetabular retroversion to prevent posterior osteoarthritis of the hip due to posterior wall deficiency.

Modified pubic osteotomy for medialization of the femoral head in periacetabular osteotomy: a retrospective study of 144 hips.

BACKGROUND AND PURPOSE: Medial displacement of the femoral head reduces the force transmitted across the hip joint. Since 2005, we have performed a modified Ganz's osteotomy with curved periacetabular osteotomy (CPO) to obtain medialization of the femoral head. The modification involves cutting of the pubis at 30 degrees to the horizontal line. Here, we examined whether this modified CPO procedure medialized the femoral head more than the conventional CPO procedure. PATIENTS AND METHODS: 69 patients (mean age 37 years, 72 hips) treated with the modified CPO procedure (the M group) were compared with 68 patients (mean age 38 years, 72 hips) previously treated with conventional CPO (the C group). All patients were operated because of dysplastic hips. We used radiographic measurements from anteroposterior radiographs. The magnitude of the resultant hip force normalized with respect to the body weight (R/WB) and hip contact joint stress (Pmax/ WB) was calculated in all cases. RESULTS: The average lateral center-edge (CE) angle, acetabular roof obliquity (ARO), and acetabulum-head index (AHI) improved in both groups. The CE angle, ARO, and AHI were similar in the 2 groups before and after surgery. Medialization of the femoral head was larger in the M group than in the C group (p < 0.001). The average value of the resultant hip force decreased from 3.2 to 2.9 in the M group and remained unchanged, at 3.1, in the C group. In addition, the average value of the peak contact stress decreased more in the M group (from 9.4 kPa/N to 3.4 kPa/N) than in the C group (from 9.1 kPa/N to 4.3 kPa/N). INTERPRETATION: In dysplastic hips, the modified CPO reduces the contact hip stress more than the conventional CPO because of better medialization of the femoral head.

Interdigital amelanotic spindle-cell melanoma mimicking an inflammatory process due to dermatophytosis.

Herein, we report a rare case of amelanotic spindle-cell melanoma on the interdigit of the left fifth toe of an 83-year-old woman. She also had tinea pedis on the same part for more than 2 years, and the part in which the tumor developed had been macerated and colonized with both Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus. Histopathologically, the biopsy specimen was indistinguishable from that of nonspecific inflammatory granulation. Two biopsies could not lead us to the correct diagnosis until the totally excised specimen was evaluated with immunohistochemical analysis including S-100 and other melanocyte markers. The patient died with multiple metastases of the tumor 18 months after her first visit. This case suggests that refractory interdigital dermatophytoses should be treated by considering the possibility of concomitant malignant neoplasms, and immunohistochemical analysis is indispensable for differential diagnosis of malignant neoplasms suggesting nonspecific granulation.

Curved periacetabular osteotomy for treatment of dysplastic hip.

UNLABELLED: The Bernese periacetabular osteotomy has a considerable rate of postoperative complications such as reflex sympathetic dystrophy, motor nerve palsy, heterotopic ossification, and delayed union of the ilium, which are assumed to be caused by extensive exposure or asphericity of the osteotomy surfaces. To address these issues, we developed the curved periacetabular osteotomy, a modification of the Bernese periacetabular osteotomy which limits dissection, prevents the outside of the ilium from being exposed, and produces osteotomy surfaces with the same curvature. Curved periacetabular osteotomies were done on 128 hips in 118 patients whose average age at the time of surgery was 35.2 years (range, 16-59 years). The average followup was 46 months (range, 24-99 months). The average center-edge angles were 4 degrees (range, -15 degrees -5 degrees ) preoperatively and 35 degrees (20 degrees -55 degrees ) postoperatively, and union of the iliac osteotomy was achieved in all hips. We experienced three asymptomatic pubic nonunions. Dysesthesias occurred in 27 patients along the lateral femoral cutaneous nerve and symptoms resolved in 23 patients within 1 year. The average Harris hip score improved from 72 to 93 points. There were no major complications such as sciatic nerve palsy, abductor dysfunction, or heterotopic ossification. LEVEL OF EVIDENCE: Therapeutic study, Level IV (case series--no, or historical control group). See the Guidelines for Authors for a complete description of levels of evidence.

A quantitative anatomic characterization of the quadrilateral surface for periacetabular osteotomy.

The periacetabular osteotomy described by Ganz et al is used widely, and includes an outward osteotomy from the quadrilateral surface. Because intraarticular extension of the osteotomy can complicate the Ganz osteotomy, it is important to image the margin of the hip. To prevent this complication, and to do this procedure more safely, 32 hemipelves from cadavers were used in the current study. Some landmarks were selected that can be clarified on the quadrilateral surface during the periacetabular osteotomy. The acetabulum was hollowed out using an acetabular reamer of the same size as each femoral head, and the margin of the penetrated hole through the acetabulum was determined using these landmarks. The posterior margin of the hip is located approximately 2 cm anterior to the sciatic notch. The anatomic guidepoint for the osteotomy of the ischium averaged 14 mm inferior to the distal margin of the hip. By clarifying the margin of the hip presumed on the quadrilateral surface in this way, the periacetabular osteotomy can be done more safely, without causing complications such as intraarticular chisel penetration.

Acute effects of hip and knee positions on motor-evoked potentials of the sciatic nerve in total hip arthroplasty.

In 23 patients, motor-evoked potentials (MEP) of the sciatic nerve were elicited during total hip arthroplasty by using a stimulating electrode at the level of the acetabulum and recording from the middle portion of the tibialis anterior. The distal motor latencies were determined before dislocation (control), during dislocation, and after reduction with the trial prosthesis. While the hip was dislocated, recording was performed at varying angles of the hip and knee joints. During dislocation, the distal motor latencies were significantly increased in all positions except at hip flexion of 60 degrees and internal rotation of 60 degrees with the knee joint in maximum flexion. No significant correlations were found between the latency increase and limb lengthening. No patient had sciatic nerve palsy or causalgia after operation.

In vivo study of acute effects of hip and knee positions on blood flow in canine sciatic nerve.

We studied blood flow in the canine sciatic nerve using a laser Doppler flowmeter. Blood flow was measured in 20 hind limbs of ten adult dogs at varying angles of hip flexion, hip rotation and knee flexion. Blood flow decreased as flexion and internal rotation of the hip increased and also with only slight flexion of the knee. With 90 degrees knee flexion, the mean blood flow did not change significantly when the hip was internally rotated from 0 degrees to 30 degrees. When the knee was straight, the blood flow changed significantly during the same procedure. To prevent sciatic nerve palsy, attention should be paid to the positioning of the hip and knee during total hip arthroplasty.