Fixation with poly-L-lactic acid screws in hip osteotomy: 68 hips followed for 18-46 months

Innominate Salter osteotomy using resorbable screws: a retrospective case series and presentation of a new concept for fixation

PURPOSE

The Salter innominate osteotomy (SIO) in children is traditionally stabilized by Kirschner-wires, which have issues regarding stability, infection and the need to be extracted. To counter these disadvantages, we present a surgical method to stabilize SIO with modern resorbable poly lactic-co-glycolic acid screws. Using a case series of 21 patients treated with SIO for developmental dysplasia of the hip or Legg-Calvé-Perthes disease we evaluate the feasibility of the method.

METHODS

The integrity of the osteotomy was interpreted by radiological measurements of acetabular index, centre-edge angle and Reimer's index. Perioperative and postoperative complications were evaluated.

RESULTS

Radiographic evaluation revealed a stable osteotomy and favourable development in all measured parameters with the exception of one patient who fell out of bed the first day postoperatively. No other perioperative surgical complications were observed and there were no local reactions to the resorbable screws.

CONCLUSION

Modern resorbable screws carry multiple benefits both for the patient and the surgeon. In our case series the implants provided sufficient stability and the implants caused no local reactions. The use of resorbable implants gave the surgeon a wider range of possible screw placements and avoided the need for implant removal.

LEVEL OF EVIDENCE

Level IV - Case series.

Biodegradability of poly(lactic-co-glycolic acid) after femtosecond laser irradiation

Biodegradation is a key property for biodegradable polymer-based tissue scaffolds because it can provide suitable space for cell growth as well as tailored sustainability depending on their role. Ultrashort pulsed lasers have been widely used for the precise processing of optically transparent materials, including biodegradable polymers. Here, we demonstrated the change in the biodegradation of a poly(lactic-co-glycolic acid) (PLGA) following irradiation with femtosecond laser pulses at different wavelengths. Microscopic observation as well as water absorption and mass change measurement revealed that the biodegradation of the PLGA varied significantly depending on the laser wavelength. There was a significant acceleration of the degradation rate upon 400 nm-laser irradiation, whereas 800 nm-laser irradiation did not induce a comparable degree of change. The X-ray photoelectron spectroscopy analysis indicated that laser pulses at the shorter wavelength dissociated the chemical bonds effectively, resulting in a higher degradation rate at an early stage of degradation.

Biomechanical stability of bioabsorbable screws for fixation of acetabular osteotomies

The purpose of this study was to compare the biomechanical stability of triple innominate osteotomies fixed with either bioabsorbable or stainless steel screws. Triple innominate osteotomies were performed on composite hemipelves and fixed with either three 4.5-mm bioabsorbable screws or three stainless steel 4.5-mm screws. Two screws were placed from the iliac wing into the acetabular fragment, and 1 screw was placed from below the acetabular fragment into the iliac wing. Eight specimens for each screw type were biomechanically tested in an anatomical position (replicating weight bearing) and in a flexed and abducted position (replicating spica cast positioning). Specimens were cyclically loaded between 10 and 450 N to simulate the hip contact force in this population. Lower screws were then removed, and specimens were tested under identical conditions. Fragment displacement (mm) and construct stiffness (N/mm) were compared with a 2-way analysis of variance (P < 0.05). There were no significant differences between materials for fragment displacement or construct stiffness. Anatomical position showed significantly less displacement than spica position for both materials. Initial displacement in the spica position was significantly less during lower loads for stainless steel fixation. Bioabsorbable screws demonstrate comparable biomechanical stability to stainless steel screws in anatomical and spica positions at physiological loads. Flexion and abduction of the femur adversely affect the stability of the construct for both materials. Bioabsorbable screws behave similarly to steel screws when stabilizing triple innominate osteotomies and would have the advantage of not requiring a second surgery for screw removal. Confirmation of biocompatibility should be completed before widespread clinical application.

Fixation with poly-L-lactide screws in hip osteotomies

The purpose of our study was to investigate the bone union rates and complication rates, including breakage of screws, infection, and osteolysis, in hip osteotomies using poly-L-lactic screws. We prospectively followed up 111 hips in 100 patients using conventional radiography, in which 81 rotational acetabular osteotomies, 26 Chiari pelvic osteotomies, and four Sugioka's transtrochanteric osteotomies were performed. The mean age of the patients at the time of surgery was 34 years, and the mean followup was 5.4 years. Eighty-one osteotomized acetabula and 98 osteotomized greater trochanters were fixed using poly-L-lactic screws. These hips were compared with 64 hips in 58 patients using metallic screws. Bone union was achieved in 80 of the 81 acetabular osteotomies, except in one hip with postoperative deep infection. Proximal displacement of the greater trochanter because of poly-L-lactic screw breakage occurred in six (6%) hips. None of the metallic screws broke. Osteolysis occurred in one hip with a trochanteric osteotomy using poly-L-lactic screws. Poly-L-lactic screws are suitable to transfix the osteotomized acetabulum, but there is some risk of fracture when used to reattach an osteotomized greater trochanter. Complete bone ingrowth in the screw channels cannot be expected for several years after insertion. Osteolysis is a possible complication.

LEVEL OF EVIDENCE

Therapeutic study, Level II (prospective comparative study). See the Guidelines for Authors for a complete description of levels of evidence.

Chiari pelvic osteotomy for advanced osteoarthritis in patients with hip dysplasia

BACKGROUND

It is not clear whether a Chiari pelvic osteotomy performed for the treatment of advanced osteoarthritis can delay the need for total hip arthroplasty. We present the mid-term results of the Chiari pelvic osteotomy performed for the treatment of Tönnis grade-3 osteoarthritis (large cysts, severe narrowing of the joint space, or severe deformity or necrosis of the head with extensive osteophyte formation), with a particular focus on whether this procedure can delay the need for total hip arthroplasty.

METHODS

We followed thirty-two hips in thirty-one patients with Tönnis grade-3 osteoarthritis who had refused total hip arthroplasty and had been treated with a Chiari pelvic osteotomy. The mean age at the time of surgery was 35.2 years. The mean duration of follow-up was 11.2 years, at which time clinical evaluation with the Harris hip score and radiographic evaluation were performed.

RESULTS

The average Harris hip score improved from 52 points preoperatively to 77 points at the time of follow-up; the average pain score improved from 20 to 31 points. Three hips with a hip score of <70 points required total hip arthroplasty. With a hip score of <70 points as the end point, the cumulative rate of survival at ten years was 72%. The clinical outcome was significantly influenced by the preoperative center-edge angle (p = 0.004), the preoperative acetabular head index (p = 0.039), achievement of the appropriate osteotomy level (p = 0.011), and superior migration (p = 0.009) and lateral migration (p = 0.026) of the femoral head.

CONCLUSIONS

Although the clinical results were inferior to those of total hip arthroplasty, Chiari pelvic osteotomy may be an option for young patients with advanced osteoarthritis who prefer a joint-conserving procedure to total hip arthroplasty and accept a clinical outcome that is predicted to be less optimal than that of total hip arthroplasty. Moderate dysplasia and moderate subluxation without complete obliteration of the joint space and a preoperative center-edge angle of at least 10 degrees are desirable selection criteria.