Research
Technique for preventing cement extrusion from screw holes during conversion of failed hip fracture fixation to total hip replacement
In vitro structural properties of braided tendon grafts
In an effort to increase strength in hamstring tendon grafts for anterior cruciate ligament reconstruction, braiding or weaving of the tendons has been suggested. The purpose of this study was to examine the biomechanical properties of two braiding techniques compared with a four-stranded tendon graft using a sheep model. Digital extensor tendons from 5 adult sheep were harvested in 28 matched pairs and randomly allocated to French plait or four-stranded weave. The grafts were tested in a hydraulic testing machine with the tendons secured in brass grips frozen with liquid carbon dioxide. The tendons were preconditioned to a distraction of 1 mm for 10 cycles followed by testing to failure at 50 mm/sec, with a data acquisition rate of 1,000 Hz. The stiffness, ultimate load to failure, and the mode of failure were recorded. All braided samples failed at the midsubstance, while the four-stranded controls failed at the grip interface. There was a significant reduction in strength and stiffness of the braided samples compared with the controls. This study demonstrated that braiding decreases the strength and stiffness of a four-stranded tendon graft by up to 54% and 85%, respectively. This finding is supported by the work of Hearle et al. (1969), who demonstrated that the decrease in strength of fiber bundles is equal to the square of the cosine of the twist angle. The twist angle in our samples was approximately 45 degrees, which equates to a decrease in strength of 50%.
The anatomically difficult primary total hip replacement: medium- to long-term results using a cementless odular stem
This prospective study presents the ten-year (5 to 16) clinical and radiological results of 55 primary total hip replacements (THR) using a cementless modular femoral component (S-ROM). All patients had a significant anatomical abnormality which rendered the primary THR difficult. The mean Harris hip score was 36 (12 to 72) pre-operatively, 83 (44 to 100) at five years, and 85 (45 to 99) at ten years. The Western Ontario and McMaster Universities osteoarthritis index (WOMAC) and short-form (SF)-12 scores were recorded from the year 2000. The mean SF-12 score at five years after surgery was 45.24 (22.74 to 56.58) for the physical component and 54.14 (29.20 to 66.61) for the mental component. By ten years the SF-12 scores were 42.86 (21.59 to 58.95) and 51.03 (33.78 to 61.40), respectively. The mean WOMAC score at five years post-operatively was 25 (0 to 59), and at ten years was 27 (2 to 70). No femoral components were radiologically loose, although five had osteolysis in Gruen zone 1, three had osteolysis in zone 7, and two showed osteolysis in both zones 1 and 7. No osteolysis was observed around or distal to the prosthetic sleeve. No femoral components were revised, although three hips underwent an acetabular revision and two required a liner exchange. At a mean of ten years’ follow-up the S-ROM femoral component implanted for an anatomically difficult primary THR has excellent clinical and radiological results.
Performance characteristics of ultrasound of the knee in a general radiological setting
Ultrasound of the musculoskeletal system is an attractive imaging modality due to the lack of ionising radiation, cost and ease of availability. A role has been established in the shoulder and pediatric hip but not in the knee. Ultrasound studies of the knee performed at six general radiological practices without established musculoskeletal expertise were compared with clinical examination in 56 patients. Final diagnoses were established by arthroscopy and/or MRI. The sensitivity and specificity for detection of superficial lesions in the knee were 88 and 41% for clinical examination and 32 and 59% for ultrasound. For deep lesions sensitivity and specificity were 61 and 64% for clinical examination and 13 and 100% for ultrasound. Ultrasound studies of the knee in a general radiological practice do not offer significant information above clinical examination.
Radiation exposure using laser aiming guide in orthopaedic procedures
BACKGROUND:
Ionizing radiation from intraoperative fluoroscopy presents a serious occupational health and safety concern to orthopaedic surgeons.The long-term effects of ionizing radiation are well known; they include damage to the eyes, increased risk of haematological malignancy and carcinomas throughout the body. We studied the effect of using an attachable laser aiming guide on radiation exposure during intraoperative fluoroscopy.
METHODS:
A prospective, randomized controlled trial was performed at a single institution. Eight hundred and eighty consecutive orthopaedic procedures involving fluoroscopy were randomized into two groups. One group had fluoroscopy without an aiming guide, the other group had fluoroscopy with the aiming guide. Total exposure time, number of exposures and the body region examined were recorded.
RESULTS:
For most regions studied, no significant difference in exposure time or number of exposures was found. For hip fractures, use of the laser aiming device was associated with an increase in the number of exposures (P = 0.035), but there was no significant difference in average exposure time (P = 0.31). Use of the aiming device was associated with an increased number of exposures (P = 0.0025) and an increased exposure time (P = 0.0016)for examination of the wrist, but this may represent selection bias. Conclusion: Use of a laser aiming device during intraoperative fluoroscopy was not associated with decreased exposure to radiation.
Patellar tendon-to-patella ratio in children
Patellofemoral problems are common in skeletally immature patients. In the evaluation of this condition, it is important to determine the position of the patella on lateral radiographs. There are no normal values to determine this ratio (patellar tendon-to-patella ratio). In this study, 225 anteroposterior (AP) and lateral radiographs of skeletally immature knees were examined and bone ages determined. The patellar tendon-to-patella ratio was then calculated for each age group until skeletal maturity. These ratios allow a more accurate assessment of patella alta in the pediatric population, assisting in diagnosis and surgical planning.
Biomechanical performance of Bankart repairs in a human cadaveric shoulder model
The objective of this study was to develop a method to evaluate the biomechanical performance of Bankart repairs in a human cadaveric shoulder in a clinically relevant orientation. Twenty fresh-frozen human cadaveric shoulder girdles were used to compare the biomechanical performance of intact anteroinferior capsulolabral complexes with the biomechanical performance of three Bankart lesion reconstruction techniques. Repairs were performed on surgically created Bankart lesions. Evaluations were performed with the shoulders in glenohumeral abduction and external rotation. The repair techniques employed interosseous sutures, Mitek GII suture anchors, or Acufex T-Fix devices. The suture material used in all repairs was No. 2 Ti-Cron. The biomechanical performance of the three reconstruction techniques did not differ, but each was significantly inferior compared with that of the intact shoulder samples. The interosseous repairs failed by suture pullout through soft tissue. Repairs in the Mitek GII group failed by pullout of the suture anchors, suture breakage, or pullout of the suture through soft tissue. Repairs in the T-Fix group failed by pullout of the suture through soft tissue or failure of the polymer portion of the T-Fix suture.
The accuracy of bone resections made during computer navigated total knee replacement. Do we resect what the computer plans we resect?
Many studies have shown that computer navigation in total knee arthroplasty aids the surgeon to place the prosthesis in a more accurate overall alignment. Bony resection creates the flexion and extension gaps; important in balancing the knee and implant selection in TKR. The computer plans the bone cuts but has variables that it cannot control: the surgeon, the saw blade thickness and oscillation, the accuracy of the jigs, movement of the pins, and the quality of initial mapping data inputted by the surgeon. The accuracy of computer navigated bone resections are validated on cadavers, but this is the first study to compare the predicted bone cuts to that physically resected during TKR. For 89 patients undergoing primary TKR, the bone cut from the distal femur and proximal tibia was measured using Vernier callipers and compared to the computer calculation of the same. Results show that computer measurement of the physical space left by the resected bone is accurate.
The influence of ambient theater temperature on cement setting time
We have prospectively recorded ambient operating theater temperature from 186 total knee arthroplasties and the time taken for the cement to set at implantation. The majority of cases used Antibiotic Simplex cement (n = 131), and the rest, Simplex with tobramycin (n = 55). Set time was defined as when a no. 15 scalpel could not indent the cement surface at either the femoral or tibial interface. There was a reasonable negative correlation between temperature and setting time (Antibiotic Simplex: Pearson correlation coefficient, R = -0.674; Simplex with tobramycin: R = -0.655). There was also a considerable variation of setting time at any given theater temperature. There is an inverse relationship between ambient theater temperature and the setting time for Simplex cement, and surgeons should be aware that the setting time can vary considerably. Their operative protocol should take this into account.
Lateral hip pain: does imaging predict response to localized injection?
Lateral hip pain is a common complaint in patients with a history of lower back pain from spinal disease. These patients often are diagnosed and treated for trochanteric bursitis because of localized pain and tenderness in the lateral hip. We presumed numerous scintigraphic features could provide diagnostic criteria for diagnosing gluteus medius tendinitis and trochanteric bursitis. A study was designed to assess the scintigraphic criteria for diagnosis of trochanteric bursitis and to evaluate the relationship of trochanteric bursitis to gluteus medius tendinitis and lumbar degenerative disease in predicting relapse after injection. We evaluated 97 patients with greater trochanteric pain syndrome to find a correlation between trochanteric bursitis, gluteus medius tendinitis, and spinal degenerative disease using scintigraphy and magnetic resonance imaging. We also evaluated predictors for responding to trochanteric injection of local anesthetic/glucocorticoid injection. We found a correlation between lumbar degenerative disease, gluteus medius tendinopathy, and trochanteric bursitis. Of these, 30 of 48 patients (63%) responded to injection of local anesthetic and glucocorticoids. The major predictor of relapse of pain after injection in 18 patients was the presence of moderate to severe lumbar degenerative disease seen on scintigraphic imaging. We propose a mechanistic model of the greater trochanteric pain syndrome to explain the interrelationship and response to therapy. Scintigraphy can provide sensitive and specific diagnoses of gluteus medius tendinitis and trochanteric bursitis.
Primary total hip arthroplasty in severe developmental dysplasia of the hip. Ten-year results using a cementless modular stem
We report the average 10-year clinical and radiographic results of 28 hips with Crowe III or IV developmental dysplasia of the hip (DDH) and a technically difficult primary hip arthroplasty using the cementless modular S-ROM stem (DePuy Orthopedics, Warsaw, Ind). Twenty-one patients required significant autologous bone grafting, 1 had a large allograft, and 6 patients required femoral shortening at the time of their total hip arthroplasty. Three patients had an intraoperative technical complication. The average preoperative Harris hip score was 37; at 10 years, 81. The Short Form 12 was 41.64 physical/54.03 mental at 10 years, and the WOMAC average score was 23 at 10 years. None of the S-ROM stems had been revised or were loose at latest follow-up. Six hips had osteolysis in Gruen zones 1 or 7 but none around or distal to the sleeve. The 10-year results of the S-ROM stem used in patients with osteoarthritis secondary to severe DDH are excellent.