Subchondral Collapse Research Articles

Calcium phosphate cement to prevent collapse in avascular necrosis of the femoral head

Subchondral and articular collapse following nontraumatic osteonecrosis of the femoral head is an important cause of osteoarthritis in patients between ages 20 and 40. Because hip arthroplasty in the younger population is prone to early wear and failure, it is paramount to prevent collapse once osteonecrosis is detected. Natural remodeling of the osteonecrotic areas by adjacent normal bone is predominated by osteoclastic resorption, which weakens the cancellous bone and allows microfractures to occur before full healing can take place. Current treatment modalities include core decompression and various adjuncts such as bone graft, mesenchymal stem cells and tantalum implants to provide structural integrity and to speed bony creeping substitution. Calcium phosphate cement has been reported in the treatment of fractures, especially depressed tibial plateau fractures. It is slow to resorb and is gradually replaced by bone, allowing prolonged support of periarticular fractures during healing. We hypothesize that calcium phosphate cement in conjunction with standard decompression of osteonecrotic femoral head lesions can prevent collapse.

The pathogenesis of osteoarthritis in cerebral palsy

The morphogenesis, remodeling, and degeneration of diarthroidial joints are directly under the control of the loading histories created by the musculoskeletal system during development and aging. The altered loading histories in individuals with cerebral palsy (CP) lead to aberrations in joint morphogenesis and an acceleration of joint degeneration. To understand this process in the hip, the normal ontogeny of the hip joint is reviewed with special attention to the mechano-biological factors associated with joint morphogenesis, endochondral ossification, and cartilage degeneration. A contrast is then made with the mechano-biological alterations observed with CP and the consequent influence on joint destruction. The features of the pathogenesis are: (1) altered muscular activity and restricted range of motion result in abnormal joint morphology, subluxation, and poor coverage of the femoral head; (2) joint incongruities created in early development cause local stress concentrations that can mechanically damage the articular cartilage; (3) the reduced magnitudes of muscular forces reduce the contact pressures at the joints, creating thinner cartilage and osteopenia; and (4) the thinner cartilage degenerates early, and subchondral bone collapse further contributes to the mechanical destruction of the remaining cartilage.

A histopathological evaluation of a concave-shaped low-intensity band on T1-weighted MR images in a subchondral insufficiency fracture of the femoral head

A 73-year-old female suffered from right hip pain without any history of antecedent trauma. The initial radiograph showed a slight narrowing of the joint space in the right hip. The patient was treated by non-weight bearing for 5 weeks. Radiographs obtained 3 months after the onset of pain showed the progression of both the joint-space narrowing and subchondral collapse at the superior portion. T1-weighted MR (magnetic resonance) images obtained 3 months after the onset revealed an irregular-shaped low-intensity area just beneath the articular cartilage as well as a low-intensity band, which was concave to the articular surface. A total hip replacement was performed. A histopathological examination revealed fracture callus and granulation tissue in the subchondral area. This subchondral fractured area was surrounded by vascular rich granulation tissue and fibrous tissue, which corresponded to the concave-shaped low-intensity band observed on the T1-weighted image.

Joint Preservation after Extensive Curettage of Knee Giant Cell Tumors

Curettage is the most attractive procedure for surgically treating a giant cell tumor because it preserves joint function. However, since many giant cell tumors compromise subchondral bone this technique can jeopardize the articular surface with subsequent fractures or collapse. We asked whether intralesional curettage of a giant cell tumor close to the knee that combined morselized bone and cortical structural allograft would preserve joint function. We retrospectively reviewed 22 patients treated with that approach. The minimum followup was 2 years (average, 48 months; range, 24-80 months). The distal femur was involved in 12 patients and proximal tibia in 10. Complications and failures were recorded and functional results evaluated with Musculoskeletal Tumor Society score. We determined survivorship using the Kaplan-Meier technique using removal of the implant as the endpoint. The survival was 85% and the average functional score 28 points. Three of the 22 patients had a local tumor recurrence and one had a partial subchondral collapse not requiring further treatment. Among the remaining patients, none had fracture, infection, or knee instability. The combination of fragmented and cortical allograft allows reconstructing the bone defect and ligaments created after extensive curettage of a knee giant cell tumor obtaining normal joint function and a high survival rate with minimal complications in a high percentage of the patients. Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Total Hip Arthroplasty for Alcoholic Osteonecrosis of the Femoral Head

Osteonecrosis of the femoral head in the setting of alcohol abuse is a potential important cause of symptomatic hip disease in young patients. All cases of uncemented primary total hip arthroplasty (THA) with a primary operative diagnosis of osteonecrosis of the femoral head secondary to alcohol abuse treated at our institution from January 1990 to February 2002 were identified. Twenty-three patients with 28 hips were identified; all patients had advanced disease (subchondral collapse) that was unresponsive to conservative treatment modalities. Within 5 years of index THA, 2 patients were lost to follow-up, and 2 patients died from causes unrelated to their surgery. The remaining 19 patients underwent 24 THAs. Unilateral THA was performed in 14 patients, and bilateral THA was performed in 5 patients. Seventeen men and 2 women with an average age of 41.8 years (range, 30-59 years) at the time of THA were included in the study. The average duration to clinical follow-up was 7.6 years. There was significant improvement in hip pain and hip function scores. Seven THAs were revised at a mean 6.7 years following index THA. Five- and 10-year implant survivorship free of revision was 96% and 64%, respectively (Kaplan-Meier Survivorship Analysis). The continued use of alcohol was associated with a slightly increased risk of failure (61% implant survivorship at 10 years in those with continued alcohol intake vs 75% 10-year survivorship in those without).

Subchondral insufficiency fracture of the femoral head after liver transplantation

A 53-year-old woman developed a subchondral insufficiency fracture of the right femoral head after undergoing a liver transplantation. Radiographs obtained at her first visit demonstrated a slight subchondral collapse in the superolateral portion of the femoral head. Magnetic resonance imaging (MRI) disclosed an irregular, discontinuous, low-intensity band on the T1-weighted image. After 7 months of conservative treatment, the hip pain and the radiograph abnormalities had both disappeared. On the follow-up T1-weighted MR image obtained 17 months after the onset, the band of low signal intensity was not obvious. A subchondral insufficiency fracture is one of the diagnoses to be considered in patients presenting with hip pain after a liver transplantation.

Biophysical stimulation in osteonecrosis of the femoral head

Osteonecrosis of the femoral head is the endpoint of a disease process that results from insufficient blood flow and bone-tissue necrosis, leading to joint instability, collapse of the femoral head, arthritis of the joint, and total hip replacement. Pain is the most frequent clinical symptom. Both bone tissue and cartilage suffer when osteonecrosis of the femoral head develops. Stimulation with pulsed electromagnetic fields (PEMFs) has been shown to be useful for enhancing bone repair and for exerting a chondroprotective effect on articular cartilage. Two Italian studies on the treatment of avascular necrosis of the femoral head with PEMFs were presented in this review. In the first study, 68 patients suffering from avascular necrosis of the femoral head were treated with PEMFs in combination with core decompression and autologous bone grafts. The second one is a retrospective analysis of the results of treatment with PEMFs of 76 hips in 66 patients with osteonecrosis of the femoral head. In both studies clinical information and diagnostic imaging were collected at the beginning of the treatment and at the time of follow up. Statistical analysis was performed using chi-square test. Both authors hypothesize that the short-term effect of PEMF stimulation may be to protect the articular cartilage from the catabolic effect of inflammation and subchondral bone-marrow edema. The long-term effect of PEMF stimulation may be to promote osteogenic activity at the necrotic area and prevent trabecular fracture and subchondral bone collapse. PEMF stimulation represents an important therapeutic opportunity to resolve the Ficat stage-I or II disease or at least to delay the time until joint replacement becomes necessary.

Cell therapy of hip osteonecrosis with autologous bone marrow grafting

Background:One of the reasons for bone remodeling leading to an insufficient creeping substitution after osteonecrosis in the femoral head may be the small number of progenitor cells in the proximal femur and the trochanteric region. Because of this lack of progenitor cells, treatment modalities should stimulate and guide bone remodeling to sufficient creeping substitution to preserve the integrity of the femoral head. Core decompression with bone graft is used frequently in the treatment of osteonecrosis of the femoral head. In the current series, grafting was done with autologous bone marrow obtained from the iliac crest of patients operated on for early stages of osteonecrosis of the hip before collapse with the hypothesis that before stage of subchondral collapse, increasing the number of progenitor cells in the proximal femur will stimulate bone remodeling and creeping substitution and thereby improve functional outcome.Materials and Methods:Between 1990 and 2000, 342 patients (534 hips) with avascular osteonecrosis at early stages (Stages I and II) were treated with core decompression and autologous bone marrow grafting obtained from the iliac crest of patients operated on for osteonecrosis of the hip. The percentage of hips affected by osteonecrosis in this series of 534 hips was 19% in patients taking corticosteroids, 28% in patients with excessive alcohol intake, and 31% in patients with sickle cell disease. The mean age of the patients at the time of decompression and autologous bone marrow grafting was 39 years (range: 16–61 years). The aspirated marrow was reduced in volume by concentration and injected into the femoral head after core decompression with a small trocar. To measure the number of progenitor cells transplanted, the fibroblast colony forming unit was used as an indicator of the stroma cell activity.Results:Patients were followed up from 8 to 18 years. The outcome was determined by the changes in the Harris hip score, progression in radiographic stages, change in volume determined by digitizing area of the necrosis on the different cuts obtained on MRI, and by the need for hip replacement. Total hip replacement was necessary in 94 hips (evolution to collapse) among the 534 hips operated before collapse (Stages I and II). Sixty-nine hips with stage I osteonecrosis of the femoral head at the time of surgery demonstrated total resolution of osteonecrosis based on preoperative and postoperative MRI studies; these hips did not show any changes on plain radiographs. Before treatment, these 69 osteonecrosis had only a marginal band like pattern as abnormal signal and a volume less than 20 cubic centimeters. The intralesional area had kept a normal signal as regards the signal of the femoral head outside the osteonecrosis area. For the 371 other hips without collapse at the most recent follow up (average 12 years), the mean preoperative volume of the osteonecrosis was 26 cm3 (minimum 12, maximum 30 cm3). The mean volume of the abnormal signal measured on MRI at the most recent follow up (mean 12 years) was 12 cm3. The abnormal signal persisting as a sequelae was seen on T1 images as an intralesional area of low intensity signal with a disappearance of the marginal band like pattern.Conclusion:According to our experience, best indication for the procedure is symptomatic hips with osteonecrosis without collapse. In some patients who had Steinberg stage III osteonecrosis (subchondral lucency, no collapse) successful outcomes (no further surgery) has been obtained between 5 to 10 years. Therefore in selected patients, even more advanced disease can be considered for core decompression. Patients who had the greater number of progenitor cells transplanted in their hips had better outcomes.

Bilateral Subchondral Insufficiency Fracture of the Femoral Head

Subchondral insufficiency fracture of the femoral head is a rarely reported lesion, often confused with osteonecrosis, transient osteoporosis of the hip, or rapidly destructive coxarthrosis. However, almost all the previous reports about this lesion have documented unilateral cases. We report the clinical and histological features of bilateral subchondral insufficiency fracture of the femoral head in a 68-year-old woman. She reported a sudden pain in her left hip without apparent trauma. An anteroposterior radiograph 2 weeks after the onset of pain in the left hip shows a subchondral collapse of the femoral head. The entire femoral head was depicted as a low intensity area on a T1-weighted image, and there was a subchondral linear pattern of low signal intensity with a convex shape to the articular surface. On T2-weighted image, the entire femoral head was depicted as a high intensity area, and on T1-weighted image, a linear low signal intensity pattern was noted. The patient underwent hemiarthroplasty. Cross-section of the femoral head showed a fracture line identified in the subchondral area. Although the patient's postoperative course was favorable, she had idiopathic pain in the right hip. A lateral radiograph 3 weeks after the onset of pain in the right hip shows irregularity at the surface of the femoral head. Cross-section of the right femoral head showed a concave fracture line in the subchondral bone. Based on these findings, bilateral subchondral insufficiency fracture of the femoral head was diagnosed.

Surgical and Molecular Advances in Osteonecrosis: Editorial Comment

Surgical and Molecular Advances in Osteonecrosis: Editorial Comment

The tantalum screw for treating femoral head necrosis: rationale and results

Femoral head necrosis (FHN) is a progressive pathology due to the failure of blood supply to the proximal femoral epiphysis, with consequent necrosis of the sub-chondral bone and collapse of the articular cartilage and loss of congruity between the head and the acetabulum. Borrowing the biological and mechanical principles from the vascularized fibular graft technique for the femoral neck, the tantalum screws have been introduced. They show an extraordinary porosity, osteoconductivity, biocompatibility and very good osteoinductivity. Vitreous tantalum can be processed to take the form of a screw, with a round medial extremity and a 25 mm threaded lateral extremity that can be inserted into the neck of the femur, thereby supporting the articular cartilage, stimulating the repair process, interrupting the interface between necrotic and healthy tissue and favoring local vascularization. We have drawn up a treatment protocol for early-stage FHN, based on the insertion of a tantalum screw into the femoral neck. The implant has a cylindrical shape, with a 10 mm diameter in the smooth part and 15 mm in the threaded part. It is available in different sizes from 70 to 130 mm, with 5 mm increments. The aim of the study is to describe the clinical and instrumental results of the tantalum screw for FHN. From June 2004 to June 2006 we performed 15 implants. The tantalum screw was inserted with an incision on the trochanteric region with traction and under X-ray control. For the clinical evaluation of the hip, we used the Harris hip score (HHS). For diagnosis and staging we used standard X-rays in two views and/or MRI, using the Steinberg classification (J Bone Joint Surg Br 77:34-41, 1995) and CT. In all cases, the osteonecrosis extended to not more than 30% of the joint surface and the cartilage was intact with no collapse. To assess the results, we compared the pre-operative and the post-operative HHS, calculated the percentage differences between the two. We then compared X-rays, CT scans and MRI before and some time after the operation to assess whether the problem had been addressed, taking into account the intracancellous edema and the possible extension of necrosis. After an average follow-up period of 15.43 +/- 5.41 months, ten implants (seven patients out of ten) were examined and all but one patient showed a marked improvement in HHS (the average increase was 127.9%), with no further progression of the disease. We believe that this procedure can be suitable for young patients with limited first or second stage osteonecrosis. The objective for the foreseeable future is to resolve the pain, improve the quality of life and prevent or at least postpone arthroplasty.

Are Fibula Strut Allografts a Reliable Alternative for Periarticular Reconstruction after Curettage for Bone Tumors?

Bone tumors occurring in periarticular locations may cause a substantial risk of subchondral fracture and collapse. Poly-methylmethacrylate has been used for reconstruction in these instances because of its immediate structural stability. Allogeneic graft allows for biologic incorporation and remodeling, but it takes longer. Adding a fibula strut graft to the construct seems to provide structural stability during incorporation of the particulate graft. Seventeen of 22 (77.3%) patients returned to their full preoperative level of function after this procedure. We believe adding fibula strut to particulate allograft when using the buttress technique provides structural integrity and biologically active reconstruction, while maintaining a recurrence rate similar to those described for other reconstruction techniques.

Intraoperative Radiation for Limb Sparing of the Distal Aspect of the Radius Without Transcarpal Plating in Five Dogs

To evaluate intraoperative irradiation (IORT) as a method of limb spare with preservation of the radiocarpal joint. Prospective case series. Dogs (n=5) with stage II sarcoma of the distal aspect of the radius. A bone segment containing the tumor was isolated surgically, treated by IORT, reimplanted, and secured by internal fixation. In 1 dog, the postradiation tumor bed was curetted and filled with bone cement. Dogs were administered alternating adriamycin and carboplatin starting 2 weeks after IORT and monitored at regular intervals. Four dogs had osteosarcoma and 1 had undifferentiated sarcoma. Implant failure (n=3), deep tissue infection (3), and pathologic fracture (3) resulted in amputation (3) or pancarpal plating (2). The dog with undifferentiated sarcoma was euthanatized because of suspected tumor recurrence 4 months postoperatively. Osteotomy healing was documented by radiography (1), histopathology (2), or by direct observation (2). A technique for limb-sparing surgery of the distal portion of the radius in dogs using IORT had advantages include healing of the autograft and a source for a perfectly fitting autograft but did not appear to offer any advantage with respect to infection rate. Long-term preservation of the radiocarpal joint was not successful. It was not possible to preserve the function of the radiocarpal joint and so this technique cannot be recommended currently. Further study is needed to evaluate whether or not IORT can be considered in combination with pancarpal plating and possibly curettage and cementation of the tumor to prevent subchondral bone collapse.

MR imaging of erosions in interphalangeal joint osteoarthritis: is all osteoarthritis erosive?

Erosive osteoarthritis is usually considered as an inflammatory subset of osteoarthritis (OA). However, an inflammatory component is now recognised in all subsets of OA, so this subgroup of erosive or inflammatory OA is more difficult to conceptualise. The aim of this study was to compare routine CR and MRI to investigate erosion numbers and morphology to determine whether hand OA in general is a more erosive disease than previously recognised. Fifteen patients with clinical (OA) of the small joints of the hand underwent MRI of one of the affected proximal interphalangeal (PIP) or distal interphalangeal (DIP) joints. Conventional radiographs (CR) of the hand were also obtained. The MR images were reviewed by two observers for the presence of central and marginal erosions. The site and morphology of any erosions was recorded. CR images of the same hand joint were scored independently for central and marginal erosions by the same observers. There was 100% agreement between the observers for scoring erosions on CR. Agreement for the MRI scores was also excellent (kappa = 0.84). MRI detected 37 erosions, of which only 9 were seen on CR. The increase in sensitivity using MRI was much greater for marginal erosions (1 detected on CR, 19 on MRI) than for central erosions (8 on CR, 18 on MRI). Using MRI 80% of joints examined showed 1 or more erosions compared with 40% using CR. If only marginal erosions were considered 80% of joints were still considered erosive by MRI criteria, but only 1 showed evidence of erosion on CR. Morphologically central erosions appeared to represent areas of subchondral collapse and pressure atrophy. In contrast, marginal erosions resembled those seen in inflammatory arthritides. Erosions, and particularly marginal erosions typical of those seen in inflammatory arthritis, are a more common feature of small joint OA than conventional radiographs have previously indicated.

BIOPHYSICAL STIMULATION WITH PULSED ELECTROMAGNETIC FIELDS IN OSTEONECROSIS OF THE FEMORAL HEAD

Background: Osteonecrosis of the femoral head is the end point of a disease process that results in bone necrosis, joint edema, and cartilage damage. It leads to joint arthritis that necessitates total hip arthroplasty in many patients. Because of its positive effects on osteogenesis and its chondroprotective effect of articular cartilage, pulsed electromagnetic field stimulation has been proposed as a method to prevent or delay the progression of osteonecrosis. Methods: A retrospective analysis of the results of treatment with pulsed electromagnetic field stimulation of seventy-six hips in sixty-six patients with osteonecrosis of the femoral head was performed. Patients with Ficat stage I, II, or III osteonecrosis of the femoral head were treated with pulsed electromagnetic field stimulation for eight hours per day for an average of five months. Clinical and diagnostic imaging information was collected at the start of the treatment and at the time of follow-up. The primary end point analyzed was the avoidance of hip surgery, and the secondary end point was limiting the radiographic progression (according to Ficat stage) of osteonecrosis of the femoral head. Results: Fifteen hips required a total hip arthroplasty; twelve of these hips were in patients with Ficat stage-III disease. The need for total hip arthroplasty was significantly higher in patients with Ficat stage-III disease than in patients with Ficat stage-I (p < 0.0001) or II (p < 0.01) disease at the beginning of treatment. Pulsed electromagnetic fields preserved 94% of Ficat stage-I or II hips. Furthermore, radiographic progression (according to Ficat stage) occurred in twenty hips (26%). Pain, present in all patients at the start of the treatment, disappeared after sixty days of stimulation in thirty-five patients (53%) and was of moderate intensity in seventeen patients (26%). Conclusions: The results of this study confirm that pulsed electromagnetic field treatment may be indicated in the early stages of osteonecrosis of the femoral head (Ficat stages I and II). Pulsed electromagnetic field stimulation may be able to either preserve the hip or delay the time until surgery. The authors hypothesize that the short-term effect of pulsed electromagnetic field stimulation may be to protect the articular cartilage from the catabolic effect of inflammation and subchondral bone-marrow edema. The long-term effect of pulsed electromagnetic field stimulation may be to promote osteogenic activity at the necrotic area and prevent trabecular fracture and subchondral bone collapse. Level of Evidence: Therapeutic Level IV. See Instructions to Authors on jbjs.org for a complete description of levels of evidence.

Bone Impaction Grafting for Corticosteroid-Associated Osteonecrosis of the Knee

Osteonecrosis of the distal portion of the femur produces a segment of dead bone in the weight-bearing portion of the femoral condyle, frequently associated with subchondral fracture and collapse and eventually resulting in secondary osteoarthritis. Treatment of these late stages of osteonecrosis in the knee can be problematic. The purpose of the present study was to evaluate a new surgical technique in which the subchondral osteonecrotic lesion is removed. The bone defect is then reconstructed with impacted bone grafts to prevent collapse and/or to regain distal femoral sphericity. In this prospective, one-surgeon study, nine consecutive knees in six patients were studied, all of which had extensive corticosteroid-associated osteonecrotic lesions of the femoral condyles. Six knees had collapsed lesions when they were initially treated. The mean age of the patients was thirty-one years. Both the clinical and radiographic outcomes were assessed at a minimal follow-up time of two years. At a mean follow-up time of fifty-one months, none of the reconstructed knees had been converted to a total knee prosthesis. The objective Knee Society score improved from a mean of 63 to 89 points. The functional Knee Society score improved from a mean of 19 to 81 points. During the follow-up period, there was no progression of collapse observed; however, three knees showed early signs of osteoarthritis. Clinical success was achieved in six of eight knees, and radiographic success was achieved in seven of nine knees. At the time of writing (at the time of midterm follow-up), this method appears attractive as a joint-preserving procedure. It is a relatively simple procedure that is not likely to interfere with future knee procedures. It appears that this technique can be effective in knees with collapse of the femoral condyle, and it may delay the need for a total knee arthroplasty. Therapeutic Level IV. See Instructions to Authors on jbjs.org for a complete description of levels of evidence.

Quality of life in children with osteosarcoma after limb salvage operation

19501 Background: There are several options for the surgical management of osteosarcoma (OS) especially in the skeletally immature patients. We evaluate the clinical results and quality of life (QOL) of OS patients with limb salvage operations. Methods: From 1996 to 2005, ten children with newly diagnosed previously untreated nonmetastatic (stage IIB) OS of extremities were reviewed. There were 5 females and 5 males. The median age was 12 years (range, 8 to 14). Tumor locations: proximal humerus in 2, proximal femur in 1, distal femur in 2, proximal tibia in 3, distal tibia in 1, and tibial shaft in 1. Patients received neoadjuvant and adjuvant chemotherapy, and local wide resection of tumor. Limb salvage procedures: intraoperative extracorporeal autogenous irradiated bone graft (IORBG) in 4 and prosthetic replacement in 6. The functional results were measured for the patients accordance with the Musculoskeletal Tumor Society rating score. Results: With a median follow up of 4 years (range, 1 to 9), 7 were continuously disease free, 2 died of disease and in one there was no evidence of disease. No local recurrence was seen. Mean functional rating scores of patients with IORBG and prosthetic replacement were 82% (range 77 to 90) and 82% (range 57 to 93), respectively. Functional results were not different between these study groups and relatively good. There was one infection in patients with prosthetic replacement. There were subchondral collapse in 2 (50%), fracture in 1 (25%) and infection in 1 (25%) with IORBG. Conclusions: Limb salvage operation with neoadjuvant chemotherapy is the optimum treatment. However there remain several problems of function after limb salvage operations, with improvement of survival of pediatric osteosarcoma patient. We should select the most suitable surgical procedure to achieve the good function of limbs as well as local control. No significant financial relationships to disclose.

Three-dimensional dynamic hip contact area and pressure distribution during activities of daily living

Estimation of the hip joint contact area and pressure distribution during activities of daily living is important in predicting joint degeneration mechanism, prosthetic implant wear, providing biomechanical rationales for preoperative planning and postoperative rehabilitation. These biomechanical data were estimated utilizing a generic hip model, the Discrete Element Analysis technique, and the in vivo hip joint contact force data. The three-dimensional joint potential contact area was obtained from the anteroposterior radiograph of a subject and the actual joint contact area and pressure distribution in eight activities of daily living were calculated. During fast, normal, and slow walking, the peak pressure of moderate magnitude was located at the lateral roof of the acetabulum during mid-stance. In standing up and sitting down, and during knee bending, the peak pressures were located at the edge of the posterior horn and the magnitude of the peak pressure during sitting down was 2.8 times that of normal walking. The peak pressure was found at the lateral roof in climbing up stairs which was higher than that in going down stairs. These results can be used to rationalize rehabilitation protocols, functional restrictions after complex acetabular reconstructions, and prosthetic component wear and fatigue test set up. The same model and analysis can provide further insight to soft tissue loading and pathology such as labral injury. When the pressure distribution on the acetabulum is inverted onto the femoral head, prediction of subchondral bone collapse associated with avascular necrosis can be achieved with improved accuracy.

54-Year-Old Man With Hip Pain

54-Year-Old Man With Hip Pain

54-Year-Old Man With Hip Pain

54-Year-Old Man With Hip Pain