Ray J. Haddad

Histologic analysis of retrieved human porous-coated total joint components.

A histologic and microradiographic analysis was performed on 90 retrieved human noncemented porous-coated total joint implants recovered from 58 patients. The specimens included 62 total knee components from 34 patients and 28 total hip components from 24 patients. All components were inserted without the use of bone cement, and in no case was the retrieved component removed due to clinically or roentgenographically apparent loosening. Approximately 92% of the total knee components and 93% of the total hip components had been in situ at least six weeks; 70% of the knee components and more than 50% of the hip components had been functional for at least nine months. The histologic sections and microradio-graphs revealed varying amounts of bone growth into or in apposition to the porous coatings. In approximately one third of the components, no bone ingrowth or apposition was observed. No component had greater than 10% of the available porous material ingrown with bone. No relationship between the degree of bone ingrowth and the length of time in situ was noted. In all components, the majority of the porous coating contained fibrous tissue that in some cases displayed orientation indicating evidence of load transmission capability. The adherence of bony tissue at the time of removal, a positive roentgenographic evaluation, or, a positive clinical presentation was not found to be a definite prognosticator of bone ingrowth. It appears that the combination of limited bone ingrowth and extensive fibrous tissue ingrowth is adequate for implant fixation.

Functional performance of the knee after intraarticular anesthesia

Ten healthy young volunteers underwent gait analysis and tests of knee joint position sense. Gait analysis included determination of stride characteristics (veloc ity, cadence, gait cycle, stride length, and single limb support time), force plate analysis, and motion analysis of the knee. The tests of joint position sense examined the ability of the subject to reproduce passive position ing of the knee and the ability to detect change in angle at the knee joint. In a double-blind manner, 10 cc of sterile fluid were injected into the left knee of each volunteer. Five received 2% lidocaine, the other five received sterile saline. All tests were then repeated. No statistically significant difference was observed in any measurement before and after injection in either test group. It is concluded that intraarticular anesthesia has no effect on gait pattern or joint proprioception as measured. Intraarticular local anesthesia is used in sports medi cine to alleviate pain during arthroscopy of the knee under local anesthetic. The possibility of permitting damage in the early postoperative period due to loss of joint position sense is addressed in this paper. The results of this study suggest that injection of local anesthetic into a joint with an intact joint capsule does not compromise joint position sense as measured in this study. Furthermore, no change in gait parameters was observed in the functional task of ambulation. It must be noted that no conclusions regarding the loss of pain sensation can be made from the results of this study. Also, no conclusions regarding competitive ac tivity can be drawn from this study.

Biologic response to hydroxylapatite-coated titanium hips: A preliminary study in dogs

Abstract Hydroxylapatite (HA)-coated and uncoated Ti-6A1-4V alloy femoral endoprostheses were evaluated in adult dogs. The femoral stems had proximal anterior, posterior, and medial pockets of either a commercially pure titanium porous coating or a grooved macrotexture. They also had a medial collar, with an inferior surface pocket of either the porous coating or the grooved macrotexture. HA-coated and uncoated specimens of each type were evaluated. The devices were placed as unilateral hemiarthroplasties in 12 dogs and remained in function for up to 52 weeks. Histologic sections from the uncoated grooved implants showed no direct bone-implant apposition in the proximal regions after up to 10 weeks; the HA-coated grooved implants demonstrated extensive direct bone-coating apposition after 5 weeks. Sections from uncoated porous implants evaluated after 10 weeks demonstrated approximately equivalent ingrowth to those sections from the HA-coated devices after 6 weeks. All HA-coated implants demonstrated consistent bone-implant apposition with no fibrous tissue interposition. The HA-coated surfaces were associated with increased bone deposition and proliferation at early implantation periods. In no histologic section examined was there any evidence of deterioration of the HA coating, nor was any separation of the coating from the substrate material observed.

A comparison of three varieties of noncemented porous-coated hip replacement

We reviewed 134 primary noncemented porous-coated total hip replacements in 125 patients: 64 were DePuy AML prostheses, 20 were Howmedica PCA and 50 were Implant Technology LSF. The prostheses had been in situ for an average of 36 months, 40 months and 24 months respectively. The average pre-operative Harris hip scores were 38.2 for AML, 33.2 for PCA, and 41.0 for the LSF prostheses. The average postoperative scores were 80.7 for AML, 83.8 for the PCA, and 91.5 for LSF. Thigh or groin pain associated with the prosthesis was present in 30% of AML, 30% PCA and 8% of the LSF cases. The clinical and radiographic review showed better early results with the LSF prostheses than the others; this seemed to be related to the implant design, which provided improved initial stability and more physiological transfer of load.

Interface mechanics and bone growth into porous Co-Cr-Mo alloy implants.

The interface mechanics and bone growth into porous Co-Cr-Mo alloy implants were evaluated. Three mean pore sizes (155, 235, and 350 microns) were studied for implants fabricated with one, two, and three layers of spherical powder particles and totally porous implants. All implants had a pore volume of 38%-40%. Ten implants were inserted transcortically in the femora of six adult mongrel dogs and were allowed to remain in situ for a period of 12 weeks. Postretrieval mechanical testing and histologic and microradiographic analyses were used to evaluate the implant systems. A statistically significant increase in interface shear strength (p less than .05) was determined as the number of powder particle layers was increased from one and two layers to three layers. However, a decrease in interface strength was determined for totally porous implants (seven to 12 particle layers) below the value for the single-porous-layer implants. Pore size, in the range investigated, was not found to influence the interface attachment strength. Neither pore size nor porous layer thickness was found to affect interface stiffness. Histologic and microradiographic sections revealed extensive mineralized bone growth deep into the pores of all implant types and often extending to the core of the one-, two- and three-layered porous-coated implants. Both mature haversian bone and less mature woven bone were found within the porous structure. Extensive but incomplete bone infiltration was found in the totally porous implants, with the remainder of the porosity filled with macrophage-laden connective tissue. No difference in the histologic response was observed as a function of pore size in any of the implant systems. Active bone labels were present at the 12-week time period, indicating continued bone remodeling.

An evaluation of skeletal attachment to LTI pyrolytic carbon, porous titanium, and carbon-coated porous titanium implants

Porous titanium, carbon-coated porous titanium, and low-temperature isotropic (LTI) pyrolytic carbon transcortical implants were placed in the femora of mongrel dogs. Mechanical and histologic analyses were performed in specimens that remained in situ for six months. Qualitative histologic results indicated that the bone formed a direct appositional interface with as-deposited LTI carbon. The bone tissue response to the two systems with porous coatings was similar. Both systems showed little fibrous tissue interposition and a high degree of mineralized bone ingrowth. The ingrown bone was well organized. However, there was some evidence that the ingrown bone mineral differed significantly from the bulk bone mineral. The only difference between carbon-coated and uncoated porous systems was a significant increase in the percentage of bone ingrowth, with carbon-coated specimens having a 4% increase in bone volume. The strength of appositional attachment to LTI carbon was shown to be at least one order of magnitude weaker than bone ingrowth attachment to the porous systems. The interface shear stiffness of the two porous systems was equivalent; however, the attachment shear strength of bone growth into carbon-coated porous titanium was significantly increased compared with that of bone growth into the uncoated porous titanium. Correlation of the percentage of bone ingrowth and pushout strength was also found to be statistically significant, suggesting that the presence of the carbon coating enhanced bone ingrowth, which resulted in significantly increased shear strengths.

Trabecular bone density and menstrual function in women runners

Osteoporosis results in decreased bone mineral mass and reduced trabecular bone density. Although its etiol ogy remains unknown, studies have revealed differen tial changes in the bone mineral densities of postmeno pausal women, anorexic women, and amenorrheic fe male athletes. Correlations have also been made be tween estrogen deficiency and osteoporosis in both premenopausal and postmenopausal women. In order to examine the possibility of osteopenia, a group of 36 female runners between the ages of 15 and 44 years were evaluated for bone mineral density, menstrual function, and dietary habits. Serum calcium, phospho rus, and parathyroid hormone (PTH) levels were also determined for each participant, as were complete blood counts. Using dual photon absorptiometry, all participants underwent a 20 minute scan of the lumbar spine with specificity to the L1-14 vertebrae. The 36 subjects included 19 oligomenorrheic and 17 eumenor rheic women. Results of bone density analyses re vealed that the oligomenorrheic runners had signifi cantly lower calibrated bone mineral density (CBMD) than their eumenorrheic counterparts (P << 0.01 ). Like wise, the PTH levels of the oligomenorrheic runners were also significantly lower (P << 0.01). Analysis of dietary logs revealed no significant differences between the dietary habits, the calcium intake, or the caloric intake of the two groups. The data from this study indicate that there is a relationship between reduced serum PTH levels and the oligomenorrheic state. The loss of the protective effect of estrogen in the oligo menorrheic runners possibly contributed to their re duced bone mineral densities and could be a contrib uting factor in osteopenia.

The simple bunion: Anatomy at the metatarsophalangeal joint of the great toe

The pathomechanics for the development of the hallux valgus deformity takes place at the first metatarsophalangeal joint-the sesamoid complex. The sesamoid complex consists of seven muscles, eight ligaments, and two sesamoid bones. When the first metatarsal escapes the complex and drifts medially, the sesamoids remain twisted in situ, several of the ligaments “fail,” and others contract. The authors propose reduction of the metatarsus primus varus by first metatarsal osteotomy and appropriate ligament releases and plications to restore alignment. A detailed understanding of the pathomechanics is essential for proper interpretation of the problems and anticipated lasting surgeries.

Comparative mechanical analysis of a looped-suture tendon repair

The in vitro breaking force of a braided nylon looped-suture tendon juncture designed to decrease tying time was compared with the breaking force of the modified Kessler and Bunnell techniques. Repaired with either braided nylon or tetrafluoroethylene, porcine digiti quarti propius tendons were tested to single cycle failure on a MTS hydraulic testing machine. The results showed that the looped-suture technique had a mean breaking force that was statistically indistinguishable from that of the Bunnell technique regardless of suture material. However, the breaking forces for the looped suture and Bunnell techniques were statistically greater for both suture materials when compared with the modified Kessler technique. The resistance to gap formation for the looped suture was found to be intermediate between the Bunnell technique and the modified Kessler technique.

Tissue growth into porous primary and revision femoral stems

The authors studied 45 uncemented porous-coated femoral stems from 45 patients: 35 primary total hip arthroplasties and 10 revisions of either cemented (7) or uncemented (3) femoral components. Histologic sections were examined quantitatively for type, amount, and distribution of tissue ingrowth; these findings were correlated with clinical and radiographic data. Fibrous tissue ingrowth predominated in both groups. Of the primary arthroplasty group, the grade of bone ingrowth in 8 specimens was none, 14 minimal, 6 moderate, and 7 more extensive. In the revision cases, the grade of bone ingrowth in 5 was none, 3 minimal, and 2 moderate. Bone ingrowth was seen more frequently in the distal porous coating, particularly in the revision cases, and most often where direct stem-endosteal canal contact had occurred. While bone ingrowth can occur in uncemented revision stems, it generally appears less abundantly than in primary total hip arthroplasty.